Reference Guide on Medical Testimony


John B. Wong, M.D., is Chief of the Division of Clinical Decision Making, Informatics, and Telemedicine at the Institute for Clinical Research and Health Policy Studies, Tufts Medical Center, and Professor of Medicine at Tufts University School of Medicine.

Lawrence O. Gostin, J.D., is Linda D. and Timothy J. O’Neill Professor of Global Health Law and Faculty Director of O’Neill Institute for National and Global Health Law, Georgetown University Law Center.

Oscar A. Cabrera, Abogado, LL.M., is Deputy Director of the O’Neill Institute for National and Global Health Law and Adjunct Professor of Law, Georgetown University Law Center.


   I. Introduction

  II. Medical Testimony Introduction

A. Medical Versus Legal Terminology

B. Applicability of Daubert v. Merrell Dow Pharmaceuticals, Inc.

C. Relationship of Medical Reasoning to Legal Reasoning

 III. Medical Care

A. Medical Education and Training

1. Medical school

2. Postgraduate training

3. Licensure and credentialing

4. Continuing medical education

B. Organization of Medical Care

C. Patient Care

1. Goals

2. Patient-physician encounters

 IV. Medical Decisionmaking

A. Diagnostic Reasoning

1. Clinical reasoning process

2. Probabilistic reasoning and Bayes’ rule

3. Causal reasoning

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Reference Guide on Medical Testimony J O H N B . W O N G , L AW R E N C E O . G O S T I N , A N D OSCAR A. CABRERA John B. Wong, M.D., is Chief of the Division of Clinical Decision Making, Informatics, and Telemedicine at the Institute for Clinical Research and Health Policy Studies, Tufts Medical Center, and Professor of Medicine at Tufts University School of Medicine. Lawrence O. Gostin, J.D., is Linda D. and Timothy J. O’Neill Professor of Global Health Law and Faculty Director of O’Neill Institute for National and Global Health Law, Georgetown University Law Center. Oscar A. Cabrera, Abogado, LL.M., is Deputy Director of the O’Neill Institute for National and Global Health Law and Adjunct Professor of Law, Georgetown University Law Center. ConTenTs I. Introduction, 689 II. Medical Testimony Introduction, 689 A. Medical Versus Legal Terminology, 689 B. Applicability of Daubert v. Merrell Dow Pharmaceuticals, Inc., 692 C. Relationship of Medical Reasoning to Legal Reasoning, 693 III. Medical Care, 695 A. Medical Education and Training, 695 1. Medical school, 695 2. Postgraduate training, 697 3. Licensure and credentialing, 698 4. Continuing medical education, 700 B. Organization of Medical Care, 700 C. Patient Care, 702 1. Goals, 702 2. Patient-physician encounters, 703 IV. Medical Decisionmaking, 704 A. Diagnostic Reasoning, 704 1. Clinical reasoning process, 705 2. Probabilistic reasoning and Bayes’ rule, 707 3. Causal reasoning, 714 687

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Reference Manual on Scientific Evidence B. Testing, 717 1. Screening, 717 2. Diagnostic testing, 719 3. Prognostic testing, 721 C. Judgment and Uncertainty in Medicine, 721 1. Variation in medical care, 721 2. Evidence-based medicine, 722 3. Hierarchy of medical evidence, 723 4. Guidelines, 726 5. Vicissitudes of therapeutic decisionmaking, 728 D. Informed Consent, 734 1. Principles and standards, 734 2. Risk communication, 737 3. Shared decisionmaking, 739 V. Summary and Future Directions, 740 Glossary of Terms, 742 References on Medical Testimony, 745 688

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Reference Guide on Medical Testimony I. Introduction Physicians are a common sight in today’s courtroom. A survey of federal judges published in 2002 indicated that medical and mental health experts constituted more than 40% of the total number of testifying experts.1 Medical evidence is a common element in product liability suits,2 workers’ compensation disputes,3 medical malpractice suits,4 and personal injury cases.5 Medical testimony may also be critical in certain kinds of criminal cases.6 The goal of this reference guide is to introduce the basic concepts of diagnostic reasoning and clinical decisionmaking, as well as the types of evidence that physicians use to make judgments as treat- ing physicians or as experts retained by one of the parties in a case. Following this introduction (Section I), Section II identifies a few overarching theoretical issues that courts face in translating the methods and techniques customary in the medical profession in a manner that will serve the court’s inquiry. Sections III and IV describe medical education and training, the organization of medical care, the elements of patient care, and the processes of diagnostic reasoning and medi- cal judgment. When relevant, each subsection includes examples from case law illustrating how the topic relates to legal issues. II. Medical Testimony Introduction A. Medical Versus Legal Terminology Because medical testimony is common in the courtroom generally and indispens- able to certain kinds of cases, courts have employed some medical terms in ways 1. Joe S. Cecil, Ten Years of Judicial Gatekeeping Under Daubert, 95 Am. J. Pub. Health S74–S80 (2005). 2. See, e.g., In re Bextra & Celebrex Mktg. Sales Practices and Prod. Liab., 524 F. Supp. 2d 1166 (N.D. Cal. 2007) (thoroughly reviewing the proffered testimony of plaintiff’s expert cardiologist and neurologist in a products liability suit alleging that defendant’s arthritis pain medication caused serious cardiovascular injury). 3. See, e.g., AT&T Alascom v. Orchitt, 161 P.3d 1232 (Alaska 2007) (affirming the decision of the state workers’ compensation board and rejecting appellant’s challenges to worker’s experts). 4. Schneider ex rel. Estate of Schneider v. Fried, 320 F.3d 396 (3d Cir. 2003) (allowing a physician to testify in a malpractice case regarding whether administering a particular drug during angioplasty was within the standard of care). 5. See, e.g., Epp v. Lauby, 715 N.W.2d 501 (Neb. 2006) (detailing the opinions of two physicians regarding whether plaintiff’s fibromyalgia resulted from an automobile accident with two defendants). 6. Medical evidence will be at issue in numerous kinds of criminal cases. See State v. Price, 171 P.3d 293 (Mont. 2007) (an assault case in which a physician testified regarding the potential for a stun gun to cause serious bodily harm); People v. Unger, 749 N.W.2d 272 (Mich. Ct. App. 2008) (a second-degree murder case involving testimony of a forensic pathologist and neuropathologist); State v. Greene, 951 So. 2d 1226 (La. Ct. App. 2007) (a child sexual battery and child rape case involving the testimony of a board-certified pediatrician). 689

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Reference Manual on Scientific Evidence that differ from their use by the medical profession. Differential diagnosis, for example, is an accepted method that a medical expert may employ to offer expert testimony that satisfies Daubert.7 In the legal context, differential diagnosis refers to a technique “in which physician first rules in all scientifically plausible causes of plaintiff’s injury, then rules out least plausible causes of injury until the most likely cause remains, thereby reaching conclusion as to whether defendant’s prod- uct caused injury. . . .”8 In the medical context, by contrast, differential diagnosis 7. See, e.g., Feliciano-Hill v. Principi, 439 F.3d 18, 25 (1st Cir. 2006) (“[W]hen an examining physician calls upon training and experience to offer a differential diagnosis . . . most courts have found no Daubert problem.”); Clausen v. M/V New Carissa, 339 F.3d 1049, 1058–59 (9th Cir. 2003) (recognizing differential diagnosis as a valid methodology); Mattis v. Carlon Elec. Prods., 295 F.3d 856, 861 (8th Cir. 2002) (“A medical opinion based upon a proper differential diagnosis is sufficiently reliable to satisfy [Daubert.]”); Westberry v. Gislaved Gummi AB, 178 F.3d 257, 262 (4th Cir. 1999) (recognizing differential diagnosis as a reliable technique). 8. Wilson v. Taser Int’l, Inc. 2008 WL 5215991, at *5 (11th Cir. Dec. 16, 2008) (“[N]onetheless, Dr. Meier did not perform a differential diagnosis or any tests on Wilson to rule out osteoporosis and these corresponding alternative mechanisms of injury. Although a medical expert need not rule out every possible alternative in order to form an opinion on causation, expert opinion testimony is properly excluded as unreliable if the doctor ‘engaged in very few standard diagnostic techniques by which doctors normally rule out alternative causes and the doctor offered no good explanation as to why his or her conclusion remained reliable’ or if ‘the defendants pointed to some likely cause of the plaintiff’s illness other than the defendants’ action and [the doctor] offered no reasonable explanation as to why he or she still believed that the defendants’ actions were a substantial factor in bringing about that illness.’”); Williams v. Allen, 542 F.3d 1326, 1333 (11th Cir. 2008) (“Williams also offered testimony from Dr. Eliot Gelwan, a psychiatrist specializing in psychopathology and differential diagnosis. Dr. Gelwan conducted a thorough investigation into Williams’ background, relying on a wide range of data sources. He conducted extensive interviews with Williams and with fourteen other individuals who knew Williams at various points in his life.”) (involving a capital murder defendant petitioning for habeus corpus offering supporting expert witness); Bland v. Verizon Wireless, L.L.C., 538 F.3d 893, 897 (8th Cir. 2008) (“Bland asserts Dr. Sprince conducted a differential diagnosis which supports Dr. Sprince’s causation opinion. We have held, ‘a medical opinion about causation, based upon a proper differential diagnosis is sufficiently reliable to satisfy Daubert.’ A ‘differential diagnosis [is] a technique that identifies the cause of a medical condition by eliminating the likely causes until the most probable cause is isolated.’”) (stating expert’s incomplete execution of differential diagnosis procedure rendered expert testimony unsatisfactory for Daubert standard) (citations omitted); Lash v. Hollis 525 F.3d 636, 640 (8th Cir. 2008) (“Further, even if the treating physician had specifically opined that the Taser discharges caused rhabdomyolysis in Lash Sr., the physician offered no explanation of a differential diagnosis or other scientific methodology tending to show that the Taser shocks were a more likely cause than the myriad other possible causes suggested by the evidence.”) (finding lack of expert testimony with differential diagnosis enough to render evidence insufficient for jury to find causation in personal injury suit); Feit v. Great West Life & Annuity Ins. Co., 271 Fed. App’x. 246, 254 (3d Cir. 2008) (“However, although this Court generally recognizes differential diagnosis as a reliable methodology the differential diagnosis must be properly performed in order to be reliable. To properly perform a differential diagnosis, an expert must perform two steps: (1) ‘Rule in’ all possible causes of Dr. Feit’s death and (2) ‘Rule out’ causes through a process of elimination whereby the last remaining potential cause is deemed the most likely cause of death.”) (ruling that district court not in error for excluding expert medical testimony that relied on an improperly performed differential diagnosis) (citations omitted); Glastetter v. Novartis Pharms. Corp., 252 F.3d 986 (8th Cir. 2001). 690

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Reference Guide on Medical Testimony refers to a set of diseases that physicians consider as possible causes for symptoms the patient is suffering or signs that the patient exhibits.9 By identifying the likely potential causes of the patient’s disease or condition and weighing the risks and benefits of additional testing or treatment, physicians then try to determine the most appropriate approach—testing, medication, or surgery, for example.10 Less commonly, courts often have used the term “differential etiology” interchangeably with differential diagnosis.11 In medicine, etiology refers to the study of causation in disease,12 but differential etiology is a legal invention not used by physicians. In general, both differential etiology and differential diagnosis are concerned with establishing or refuting causation between an external cause and a plaintiff’s condition. Depending on the type of case and the legal standard, a medical expert may testify in regard to specific causation, general causation, or both. General causation refers to whether the plaintiff’s injury could have been caused by the defendant, or a product produced by the defendant, while specific causation is established only when the defendant’s action or product actually caused the harm.13 An opinion by a testifying physician may be offered in support of both kinds of causation.14 Courts also refer to medical certainty or probability in ways that differ from their use in medicine. The standards “reasonable medical certainty” and “reason- able medical probability” are also terms of art in the law that have no analog for a practicing physician.15 As is detailed in Section IV, diagnostic reasoning and medi- 9. Steadman’s Medical Dictionary 531 (28th ed. 2006) (defining differential diagnosis as “the determination of which of two or more diseases with similar symptoms is the one from which the patient is suffering, by a systematic comparison and contrasting of the clinical findings.”). 10. The Concise Dictionary of Medical-Legal Terms 36 (1998) (definition of differential diagnosis). 11. See Proctor v. Fluor Enters., Inc. 494 F.3d 1337 (11th Cir. 2007) (testifying medical expert employed differential etiology to reach a conclusion regarding the cause of plaintiff’s stroke). But see McClain v. Metabolife Int’l, Inc., 401 F.3d 1233, 1252 (11th Cir. 2005) (distinguishing differential diagnosis from differential etiology, with the former closer to the medical definition and the latter employed as a technique to determine external causation). 12. Steadman’s Medical Dictionary 675 (28th ed. 2006) (defining etiology as “the science and study of the causes of disease and their mode of operation. . . .”). For a discussion of the term “etiology” in epidemiology studies, see Michael D. Green et al., Reference Guide on Epidemiology, Section I, in this manual. 13. See Amorgianos v. Nat’l R.R. Passenger Corp., 303 F.3d 256, 268 (2d Cir. 2002). 14. See, e.g., Ruggiero v. Warner-Lambert Co. 424 F.3d 249 (2d Cir. 2005) (excluding testifying expert’s differential diagnosis in support of a theory of general causation because it was not supported by sufficient evidence). 15. See, e.g., Dallas v. Burlington N., Inc., 689 P.2d 273, 277 (Mont. 1984) (“‘[R]easonable medical certainty’ standard; the term is not well understood by the medical profession. Little, if anything, is ‘certain’ in science. The term was adopted in law to assure that testimony received by the fact finder was not merely conjectural but rather was sufficiently probative to be reliable”). This reference guide will not probe substantive legal standards in any detail, but there are substantive differences in admissibility standards for medical evidence between federal and state courts. See Robin Dundis Craig, When Daubert Gets Erie: Medical Certainty and Medical Expert Testimony in Federal Court, 77 Denv. U. L. Rev. 69 (1999). 691

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Reference Manual on Scientific Evidence cal evidence are aimed at recommending the best therapeutic option for a patient. Although most courts have interpreted “reasonable medical certainty” to mean a preponderance of the evidence,16 physicians often work with multiple hypotheses while diagnosing and treating a patient without any “standard of proof ” to satisfy. Statutes and administrative regulations may also contain terms that are bor- rowed, often imperfectly, from the medical profession. In these cases, the court may need to examine the intent of the legislature and the term’s usage in the medical profession.17 If no intent is apparent, the court may need to determine whether the medical definition is the most appropriate one to apply to the statu- tory language. Whether the language is a term of art or a question of law will often dictate the admissibility and weight of evidence.18 B. Applicability of Daubert v. Merrell Dow Pharmaceuticals, Inc. The Supreme Court’s decision in Daubert v. Merrell Dow Pharmaceuticals, Inc.,19 changed the way that judges screen expert testimony. A 2002 study by the RAND Corporation indicated that after Daubert, judges began scrutinizing expert testi- mony much more closely and began more aggressively excluding evidence that does not meet its standards.20 Despite the Court’s subsequent decisions in General Electric Co. v. Joiner21 and Kumho Tire Co. v. Carmichael22 further defining the 16. See, e.g., Sharpe v. United States, 230 F.R.D. 452, 460 (E.D. Va. 2005) (“It is not enough for the plaintiff’s expert to testify that the defendant’s negligence might or may have caused the injury on which the plaintiff bases her claim. The expert must establish that the defendant’s negligence was ‘more likely’ or ‘more probably’ the cause of the plaintiff’s injury . . . ”). 17. See, e.g., Feltner v. Lamar Adver., Inc., 83 F. App’x 101 (6th Cir. 2003) (holding that the statutory definition of “permanent total disability” under the Tennessee Workers Compensation Act was not the same as the medical definition); Endorf v. Bohlender, 995 P.2d 896 (Kan. Ct. App. 2000) (a medical malpractice case reversing a lower court’s interpretation of the statutory phrase “clinical practice” because it did not comport with the legislature’s intent that the statutory meaning reflect the medical definition). 18. See, e.g., Coleman v. Workers’ Comp. Appeal Bd. (Ind. Hosp.), 842 A.2d 349 (Pa. 2004) (holding that since the legislature did not define the medical term “physical examination,” the common usage of the term is more appropriate than the strict medical definition). 19. 509 U.S. 579 (1993). 20. Lloyd Dixon & Brian Gill, Changes in the Standards for Admitting Expert Evidence in Federal Civil Cases Since the Daubert Decision (2002). 21. 522 U.S. 136 (1997) (holding that the trial court had properly excluded expert testimony extrapolated from animal studies and epidemiological studies). 22. 526 U.S. 137 (1999). In Kumho, the Court made clear that Daubert applies to all expert testimony and not just “scientific” testimony. Although the case involved a defect in tires, courts before Kumho were divided on whether expert medical opinion based on experience or clinical medical testimony were subject to Daubert. See also Joe S. Cecil, Ten Years of Judicial Gatekeeping Under Daubert, 95 Am. J. Pub. Health S74–S80 (2005). See also Lawrence O. Gostin, Public Health Law: Power, Duty, Restraint (2d ed. 2008). 692

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Reference Guide on Medical Testimony Daubert standard, federal and state courts have sometimes employed conflicting interpretations of what Daubert requires from testifying physicians. The standard of review is an important factor in understanding how Daubert has engendered seemingly inconsistent results. The Supreme Court adopted an abuse of discretion standard in Joiner23 and affirmed it in Kumho.24 Although in most product liability cases the courts reached the same conclusion, inconsistent determinations regarding the admissibility of similar evidence may not constitute an abuse of discretion under the federal standard of review or in states with a similar standard.25 C. Relationship of Medical Reasoning to Legal Reasoning As Section II.A suggested, the goal that guides the physician—recommending the best therapeutic options for the patient—means that diagnostic reasoning and the process of ongoing patient care and treatment involve probabilistic judgments concerning several working hypotheses, often simultaneously. When a court requires a testifying physician to offer evidence “to a reasonable medical certainty” or “reasonable medical probability,” it is supplying the expert with a legal rule to which his or her testimony must conform.26 In other words, a lawyer often will 23. 522 U.S. at 143. 24. 526 U.S. at 142. 25. Hollander v. Sandoz Pharm. Corp., 289 F.3d 1193, 1207 (10th Cir. 2002); see also Brasher v. Sandoz Pharm. Corp., 160 F. Supp. 2d 1291, 1298 n.17 (N.D. Ala. 2001); Reichert v. Phipps, 84 P.3d 353, 358 (Wyo. 2004). 26. Courts have occasionally noted the tension between the medical reasoning and legal reasoning when applying the reasonable medical certainty or reasonable medical probability standards. See Clark v. Arizona, 548 U.S. 735, 777 (2006) (“When . . . ‘ultimate issue’ questions are formulated by the law and put to the expert witness who must then say ‘yea’ or ‘nay,’ then the expert witness is required to make a leap in logic. He no longer addresses himself to medical concepts but instead must infer or intuit what is in fact unspeakable, namely, the probable relationship between medical concepts and legal or moral constructs such as free will. These impermissible leaps in logic made by expert witnesses confuse the jury. . . .”); Rios v. City of San Jose, 2008 U.S. Dist. LEXIS 84923, at *4 (N.D. Cal. Oct. 9, 2008) (“In their fifth motion, plaintiffs seek to exclude the testimony of Dr. Brian Peterson who defendants designated to testify, among other subjects, about the ‘proximate cause’ of Rios’ death. As the use of terms that also carry legal significance could confuse the jury, the motion is granted in part, and defendants are instructed to distinguish between medical and legal terms such as proximate cause to the extent possible. Where such terms must be used by the witness consistent with the language employed in his field of expertise, the parties shall craft a limiting instruction to advise the jury of the distinction between those terms and the issues they will be called upon to determine.”); Norland v. Wash. Gen. Hosp., 461 F.2d 694, 697 (8th Cir. 1972) (“The use of the terms ‘probable’ and ‘possible’ as a basis for test of qualification or lack of qualification in respect to a medical opinion has frequently converted this aspect of a trial into a mere semantic ritual or hassle. The courts have come to recognize that the competency of a physician’s testimony cannot soundly be permitted to turn on a mechanical rule of law as to which of the two terms he has employed. Regardless of which term he may have used, if his testimony is such in nature and basis of hypothesis as to judicially impress that the opinion expressed represents his professional judgment as to the most likely one among the 693

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Reference Manual on Scientific Evidence need to explain the legal standard to the physician, who will then shape the form and content of his or her testimony in a manner that serves the legal inquiry.27 Legal standards will shape how physicians testify in a number of other ways. Although treating physicians generally are concerned less about discovering the actual causes of the disease than treating the patient, the testifying medical expert will need to tailor his or her opinions in a way that conforms to the legal stan- dard of causation. As Section IV will demonstrate, when analyzing the patient’s symptoms and making a judgment based on the available medical evidence, a physician will not expressly identify a “proximate cause” or “substantial factor.” For example, in order to recommend treatment, a physician does not necessarily need to determine whether a patient’s lung ailment was more likely the result of a long history of tobacco use or prolonged exposure to asbestos if the optimal treatment is the same. In contrast, when testifying as an expert in a case in which an employee with a long history of tobacco use is suing his employer for possible injuries as a result of asbestos exposure in the workplace, physicians may need to make judgments regarding the likelihood that either tobacco or asbestos—or both—could have contributed to the injury.28 Physicians often will be asked to testify about patients from whom they have never taken a medical history or examined and make estimates about proximate cause, increased risk of injury, or likely future injuries.29 The doctor may even need to make medical judgments about a deceased litigant.30 Testifying in all such cases requires making judgments that physicians do not ordinarily make in their profession, making these judgments outside of physicians’ customary patient encounters, and adapting the opinion in a way that fits the legal standard. The purpose of this guide is not to describe or recommend competing legal standards, whether it be the standard of proof, causation, admissibility, or the applicable stan- dard of care in medical malpractice cases. Instead, it aims to introduce the practice of medicine to federal and state judges, emphasizing the tools and methods that possible causes of the physical condition involved, the court is entitled to admit the opinion and leave its weight to the jury.”). 27. There are several cases that demonstrate the difficulty that physicians sometimes have in adapting their testimony to the legal standard. See Schrantz v. Luancing, 527 A.2d 967 (N.J. Super. Ct. Law Div. 1986) (malpractice case in which the medical expert’s opinion was inadequate because of her understanding of “reasonable medical certainty”). 28. Physicians will testify as experts in cases in which the plaintiff’s condition may be the result of multiple causes. In these cases, the divergence between medical reasoning and legal reasoning are very apparent. See, e.g., Tompkin v. Philip Morris USA, Inc., 362 F.3d 882 (6th Cir. 2004) (affirming district court’s conclusion that testimony offered by the defendant’s expert regarding the decedent’s work-related asbestos exposure was not prejudicial in a suit against a tobacco company on behalf of plaintiff’s deceased husband); Mobil Oil Corp. v. Bailey, 187 S.W.3d 265 (Tex. Ct. App. 2006) (involving claims from a worker who had a long history of tobacco use that exposure to asbestos increased his risk of cancer). 29. See, e.g., Tompkin, 362 F.3d 882. 30. See, e.g., id. 694

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Reference Guide on Medical Testimony doctors use to make decisions and highlighting the challenges in adapting them when testifying as medical experts. Sections III and IV of this guide explain in great detail the practice of medicine, including medical education, the structure of health care, and, most importantly, the methods that physicians use to diagnose and treat their patients. Special attention is given to the physician–patient relationship and to the types of evidence that physicians use to make medical judgments. In an effort to make each issue more salient, examples from case law are offered when they are illustrative. III. Medical Care A. Medical Education and Training 1. Medical school The Association of American Medical Colleges (AAMC) consists of 133 accred- ited U.S. medical schools and 17 Canadian medical schools.31 The Liaison Com- mittee on Medical Education performs the accreditation for AAMC and assesses the quality of postsecondary education by determining whether each institution or program meets established standards for function, structure, and performance. The goal of medical school is to prepare students in the art and science of medicine for graduate medical education.32 Of the 4 years of medical school, the first 2 years are typically spent studying preclinical basic sciences involving the study of the normal structure and function of human systems (e.g., through anatomy, biochemistry, physiology, behavioral science, and neuroscience), followed by the study of abnormalities and therapeutic principles (e.g., through microbiology, immunol- ogy, pharmacology, and pathology). The final 2 years involve clinical experience, including rotations in patient care settings such as clinics or hospitals with required “core” clerkships in internal medicine, pediatrics, psychiatry, surgery, obstetrics/ gynecology, and family medicine. All physicians who wish to be licensed must pass the United States Medical Licensing Examination Steps 1, 2, and 3.33 31. Association of American Medical Colleges, Membership, available at about/membership/ (last visited Feb. 12, 2011). 32. See Davis v. Houston Cnty., Ala. Bd. of Educ., 2008 WL 410619 (M.D. Ala. Feb. 13, 2008) (finding that an individual with no medical training was not qualified to give expert testimony). 33. Planned Parenthood Cincinnati Region v. Taft 444 F.3d 502, 515 (6th Cir. 2006), (“The State has not appealed the district court’s order refusing to recognize Dr. Crockett as an expert in the critical review of medical literature. Although that order has not been placed before us, the only reason the district court gave for her ruling was that Dr. Crockett did not have any specific training in the critical review of medical literature beyond the training incorporated in her general medical school and residency training. This ruling ignored Dr. Crockett’s testimony that her residency program at Georgetown University put particular emphasis on training residents in the critical review of medical literature, that she had taught classes on the subject, that she had done extensive reading and 695

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Reference Manual on Scientific Evidence In the United States, besides the more than 941,000 physicians, there are more than 61,000 doctors of osteopathy. The Commission on Osteopathic Col- lege Accreditation accredits 25 colleges of osteopathic medicine. Training is similar to that for medical physicians but with additional “special attention on the musculoskeletal system which reflects and influences the condition of all other body systems.”34 About 25% of current U.S. physicians are foreign medical gradu- ates that include both U.S. citizens and foreign nationals.35 Because educational standards and curricula outside the United States and Canada vary, the Education Commission for Foreign Medical Graduates has developed a certification exam to assess whether these graduates may enter Accreditation Council for Graduate Medical Education (ACGME) accredited residency and fellowship programs.36 self-education on the subject, and that she had critically reviewed medical literature for the FDA. If these qualifications are not sufficient to demonstrate expertise, this court is hard-pressed to imagine what qualifications would suffice.”); Davis v. Houston Cnty., Ala. Bd. of Educ., 2008 WL 410619, at *4 (M.D. Ala. Feb. 13, 2008) (“The Board has moved to exclude all evidence of Freet’s opinions and conclusions related to the cause of Joshua Davis’s behavior at the football game contained in his deposition as well as Freet’s letter to Malcolm Newman. The Board argues that Freet is not qualified to give expert testimony, and that Plaintiff failed to comply with Fed. R. Civ. P. 26(a)(2)(B) by not providing a report of Freet’s testimony that includes all of the information required by Rule 26(a) (2)(B). . . . In order to consider Freet’s expert opinions, this Court must find that Freet meets the requirements of Fed. R. Evid. 702. Rule 702 requires an expert to be qualified by ‘knowledge, skill, experience, training, or education.’ Freet is not a medical doctor and never attended medical school. The only evidence of Freet’s qualifications are: approximately five years working for the Department of Veterans Affairs in the vocational rehabilitation program, followed by approximately seven years working in private practice as a ‘licensed professional counselor.’ There is no evidence in the record of Freet’s educational background, or any details of the exact nature of Freet’s work experience.”); Therrien v. Town of Jay, 489 F. Supp. 2d 116, 117 (D. Me. 2007) (“Citing Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S. Ct. 2786, 125 L. Ed. 2d 469 (1993) and Rule 702 of the Federal Rules of Evidence, Officer Gould’s first objection is that Dr. Harding does not possess sufficient expertise to express expert opinions about ‘the mechanism and timing of Plaintiff’s injuries.’ This objection is not well taken. Dr. Harding was graduated from Dartmouth College and Georgetown Medical School; he completed a residency in internal medicine, is board certified in internal medicine, and has been licensed to practice medicine in the state of Maine since 1978.”). United States Medical Licensing Examination, Examinations, available at (last visited Aug. 9, 2011). 34. Association of American Medical Colleges, What is a DO? available at http://www. (last visited Feb. 12, 2011); Association of American Medical Colleges, About Osteopathic Medicine, available at http:// (last visited Feb. 12, 2011). 35. American Medical Association, Physician Characteristics and Distribution in the U.S. (2009). 36. Commission for Foreign Medical Graduates, About ECFMG, available at http://www.ecfmg. org/about.html (last visited Feb. 12, 2011). 696

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Reference Guide on Medical Testimony 2. Postgraduate training After graduating from medical school, most physicians undergo additional training in a residency program in a chosen specialty.37 Residencies typically range from 3 to 7 years at teaching hospitals and academic medical centers where residents care for patients while being supervised by physician faculty and participating in educational and research activities.38 After graduating from an accredited residency program, physicians become eligible to take their board certification examinations.39 Physician licensure in many states requires the completion of a residency program accredited by the ACGME, the organization which is responsible for accrediting the more than 8700 residency programs in 26 specialties and 130 subspecialties.40 Follow- ing residency, some physicians opt for additional subspecialty fellowship training. ACGME divides fellowship training41 into (1) Dependent Subspecialty Programs in which the program functions in conjunction with an accredited specialty/core program and (2) Independent Subspecialty Programs in which the program does not depend on the accreditation status of a specialty program.42 For osteopathic physicians, the American Osteopathic Association approves osteopathic postdoctoral 37. See Brown v. Harmot Med. Ctr., 2008 WL 55999 (W.D. Pa. Jan. 3, 2008). American Medical Association, Requirements for Becoming a Physician, available at ama/pub/education-careers/ (last visited Aug. 9, 2011). 38. See Planned Parenthood Cincinnati Region v. Taft, 444 F.3d 502, 515 (6th Cir. 2006). American Medical Association, Requirements for Becoming a Physician, available at http://www.ama- (last visited Aug. 9, 2011). 39. See Therrien v. Town of Jay, 489 F. Supp. 2d 116, 117 (D. Me. 2007) (finding that a physician who completed a residency in internal medicine was qualified to give his opinion on trauma related to a § 1983 claim against a police department). American Medical Association, Requirements for Becoming a Physician, available at (last visited Aug. 9, 2011). 40. Accreditation Council for Graduate Medical Education, The ACMGE at a Glance, available at (last visited Feb. 12, 2011). 41. Accreditation Council for Graduate Medical Education, Specialty Programs with Dependent and Independent Subspecialties, available at sh_progs_depIndSubs.asp (last visited Feb. 12, 2011). 42. John Doe 21 v. Sec’y of Health and Human Servs., 84 Fed. Cl. 19, 35–36 (Fed. Cl. 2008) (“The Government’s expert, Dr. Wiznitzer, is a board-certified neurologist by the American Board of Psychiatry and Neurology, with a special qualification in Child Neurology. In addition, Dr. Wiznitzer is certified by the American Board of Pediatrics. Since 1986, Dr. Wiznitzer has been an Associate Pediatrician and an Associate Neurologist at University Hospital of Cleveland, Ohio. And, since 1992, Dr. Wiznitzer has been Director of the Autism Center at Rainbow Babies and Children’s Hospital in Cleveland, Ohio. During the past 24 years, Dr. Wiznitzer also has been an Associate Professor of Pediatrics and Associate Professor of Neurology at Case Western Reserve University. Dr. Wiznitzer completed his residency in Pediatrics from Children’s Hospital Medical Center in Cincinnati and served as a Fellow in Developmental Disorders, Pediatric Neurology, and Higher Cortical Functions. Dr. Wiznitzer also has received numerous awards and honors in the neurology field and his work has been widely published.”) (citations omitted); Brown v. Hamot Med. Ctr., 2008 WL 55999, at *8–9 697

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Reference Manual on Scientific Evidence Another physician seeing the same patient subsequently ordered a PSA without any patient discussion. The PSA was high and the patient was diagnosed with incurable advanced prostate cancer. The plaintiff’s attorney argued that despite the guidelines above, the standard of care in Virginia was to order the blood test without discussion, based on four physician witnesses. The jury ruled in favor of the plaintiff.211 To illustrate the importance of patient preferences, a woman with breast cancer described her experience: “But as the surgeon diagramed incision points on my chest with a felt-tip pen, my husband asked a question: Is it really necessary to transfer this back muscle? The doctor’s answer shocked us. No, he said, he could simply operate on my chest. That would cut surgery and recovery time in half. He had planned the more complicated procedure because he thought it would have the best cosmetic result. ‘I assumed that’s what you wanted.’”212 Instead the woman preferred the less invasive approach that shortened her recovery time. In the research setting, a randomized trial with and without informed consent demonstrated that the process of getting informed consent altered the effect of a placebo when given to patients with insomnia. The first patient of each pair was randomized to no informed consent and the second to informed consent. Out of 56 patients randomized to informed consent, 26 declined to participate in the study (the patients without informed consent had no choice and were unaware of their participation in a study). The informed consent process created a “biased” group because the age and gender for those who declined participation differed significantly from those who did agree to be included in the study. The hypnotic activity of placebo was significantly higher without informed consent, and adverse events were found more commonly in the group receiving informed consent. The study suggests that the process of getting informed consent introduced biases in the patient population and affected the efficacy and adverse effects observed in this clinical trial, thereby potentially affecting the general applicability of any findings involving informed consent.213 Besides physicians, patients may get health information from the Internet, family, friends, and the media (newspapers, magazines, television). Among Internet users, 80% had searched for information on at least 1 of 15 major health topics but use varied from 62% to 89% by age, gender, education, or race/ethnicity.214 Conducted between November 2006 and May 2007, a cross-sectional national survey of U.S. adults who had made a medical decision found that Internet use 211. King & Moulton, supra note 206, at 432–34; Daniel Merenstein, A Piece of My Mind: Winners and Losers, 291 JAMA 15–16 (2004). 212. Julie Halpert, Health: What Do Patients Want? Newsweek, Apr. 28, 2003, at 63–64. 213. R. Dahan et al., Does Informed Consent Influence Therapeutic Outcome? A Clinical Trial of the Hypnotic Activity of Placebo in Patients Admitted to Hospital, 293 Brit. Med. J. Clin. Res. Ed. 363–64 (1986). 214. Pew Internet, Health Topics, (last visited Feb. 12, 2011). 736

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Reference Guide on Medical Testimony averaged 28% but varied from 17% for breast cancer screening to 48% for hip/ knee replacement among those 40 years of age and older.215 However, even among Internet users, health care providers were felt to be the most influential source of information for medical decisions, followed by the Internet, family and friends, and then media. 2. Risk communication Multiple health outcomes may result from alternative treatment choices, and how patients feel about the relative importance of those outcomes varies.216 When patients with recently diagnosed curable prostate cancer were presented with 93 possible questions that might be important to patients like themselves, 91 of the questions were cited as relevant to at least one patient.217 Communication skills should include patient problem assessment (appropriate questioning tech- niques, seeking patient’s beliefs, checking patient’s understanding of the problem); patient education and counseling (eliciting patient’s perspective, providing clear instructions and explanations, assessing understanding); negotiation and shared decisionmaking (surveying problems and delineating options, arriving at mutually acceptable solutions); relationship development and maintenance (encouraging patient expression, communicating a supportive attitude, explaining any jargon, and using nonverbal behavior to enhance communication).218 Certain forms of risk communication, however, may be confusing and should be avoided: “single event probabilities, conditional probabilities (such as sensitivity and specificity), and relative risks.”219 An example of a single-event probability would be the statement that a particular medication results in a 30% to 50% chance of developing erectile dysfunction.220 Although physicians are referring to patients, patients may misinterpret this as referring to their own sexual encounters and having an erectile dysfunction problem in 30% to 50% of their sexual encounters. The preferred natural frequency statement would be “out of 100 people like you taking this medication, 30 to 50 of them experience erectile dysfunction.” The natural frequency statement specifies a reference class, thereby reducing misunderstanding.221 215. Mick P. Couper et al., Use of the Internet and Ratings of Information Sources for Medical Decisions: Results from the DECISIONS Survey, 30 Med. Decision Making 106S–14S (2010). 216. 1983 Kassirer, supra note 203, at 889. . 1983 217. Deb Feldman-Stewart et al., What Questions Do Patients with Curable Prostate Cancer Want Answered? 20 Med. Decision Making 7–19 (2000). 218. Michael J. Yedidia et al., Effect of Communications Training on Medical Student Performance, . Michael 290 JAMA 1157–65 (2003). 219. Gerd Gigerenzer & Adrian Edwards, Simple Tools for Understanding Risks: From Innumeracy to Insight, 327 BMJ 741–44 (2003). 220. Gigerenzer, supra note 87, at 4. 221. Id. at 4; see also Section IV.A.2. 737

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Reference Manual on Scientific Evidence Regarding relative risk, consider a statement that taking a cholesterol-lowering medication reduces the risk of dying by 22%.222 This may be misinterpreted as say- ing that out of 1000 patients with high cholesterol, 220 of them can avoid dying by taking cholesterol-lowering medications. The actual data show that 32 deaths occur among 1000 patients taking the medication, and 41 deaths occur among 1000 patients taking the placebo. The relative risk reduction equals 9 divided by 41. A preferred way to express the benefit would be the absolute risk reduction (the difference between 41 and 32 deaths in 1000 patients), or to say that in 1000 people like you with high cholesterol, taking a cholesterol medication for 5 years helps 9 of them avoid dying.223 Calculating an odds ratio, the cholesterol-lowering medication reduces the odds of dying by 23%; notice that neither the relative risk nor the odds ratio characterizes the number of events without treatment and that the odds ratio always magnifies the risk or benefit when compared with the rela- tive risk. To illustrate further, a relative risk reduction of 20% has very different absolute risk reductions depending on the number of events without treatment. If 20 of 100 patients without treatment would die, then the absolute risk reduction is 4 of 100 or 4% (20% times 20), but if 20 of 100,000 patients without treatment would die, then the absolute reduction is 4 of 100,000 or 0.004%. The number needed to treat is an additional form of risk communication popularized as part of evidence-based medicine to account for the risk without treatment. It is the recip- rocal of the absolute risk difference or 1 divided by the quantity 9 lives saved per 1000 (1 ÷ (9/1000)) treated with cholesterol medications in the above example. Therefore 111 patients need to be treated with a cholesterol medication for 5 years to save one of them, or in the illustrative example, with a relative risk reduction of 20%, either 25 or 25,000 would need to be treated to save 1 patient. In the analysis of mammography for the U.S. Preventive Services Task Force, the number needed to be invited (NNI) for screening to avoid one breast cancer death was 1904 for 39- to 49-year-olds, 1339 for 50- to 59-year-olds, and 377 for 60- to 69-year-olds.224 To account for possible harm, there is a correspond- ing determination of the number needed to harm (NNH) that is calculated in the same manner. Considering breast biopsy as a morbidity, 5 women need to undergo breast biopsy for every one woman diagnosed with breast cancer for 39- to 49-year-olds, and the corresponding numbers are 3 for women ages 50 to 59 and 2 for women ages 60 to 69 years old.225 Estimates of overdiagnosis ranged mostly from 1% to 10%, and so, out of 100 women diagnosed with breast cancer from screening, 1 to 10 of them undergo treatment for a cancer that would never have caused any mortality.226 Clearly no one can tell if any particular woman has 222. Gigerenzer, supra note 87, at 34. Gigerenzer, 223. Id. at 34–35. 224. Heidi D. Nelson et al., Screening for Breast Cancer: An Update for the U.S. Preventive Services Task Force, 151 Annals Internal Med. 727–37 (2009). 225. Id. at 732. 226. Id. at 731–732 738

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Reference Guide on Medical Testimony been overdiagnosed because this is unobservable.227 The estimated extent of over- diagnosis requires estimating mortality reductions in a screened population com- pared with an unscreened population over a long period. The difference between the two groups provides an estimate of the extent of overdiagnosis. To summarize the evidence, “Mammography does save lives, more effectively among older women, but does cause some harm. Do the benefits justify the risks? The misplaced propaganda battle seems to now rest on the ratio of the risks of sav- ing a life compared with the risk of overdiagnosis, two very low percentages that are imprecisely estimated and depend on age and length of followup.”228 In the USPSTF recommendations for mammography in 40- to 49-year-olds, the focus has been on the first part of their statement “The USPSTF recommends against routine screening mammography in women aged 40 to 49 years.” Although screening has demonstrated benefits, in their view, the benefits of screening do not sufficiently and clearly outweigh the potential harms to make a recommendation that all women 40 to 49 years old have routine screening mammography from a public health or population perspective. Oft neglected, the USPSTF in their immediately subsequent sentence recognizes that individual preferences should affect the care that patients receive: “The decision to start regular, biennial screen- ing mammography before the age of 50 years should be an individual one and take patient context into account, including the patient’s values regarding specific benefits and harms.”229 The recommendation recognizes that depending on their experiences, values, and preferences, some women may seek the benefit in reduc- ing breast cancer deaths and others may prefer to avoid possible morbidity (breast biopsy and worry) and potential overdiagnosis and overtreatment. 3. Shared Decisionmaking The “professional values of competence, expertise, empathy, honesty, and commit- ment are all relevant to communicating risk: Getting the facts right and conveying them in an understandable way are not enough.”230 Shared and informed decision- making has emerged as one part of patient care. It distinguishes “problem solving” that identifies one “right” course that leaves little room for patient involvement from “decisionmaking” in which several courses of action may be reasonable and in which patient involvement should determine the optimal choice. In such cases, health care choices depend not only on the likelihood of alternative outcomes resulting from each strategy but also on the patient preferences for possible out- comes and their attitudes about risk taking to improve future survival or quality 227. Klim McPherson, Screening for Breast Cancer—Balancing the Debate, 341 BMJ 234–35 (2010). 228. Id. at 234. 229. U.S. Preventive Services Task Force, Screening for Breast Cancer: U.S. Preventive Services Task Force Recommendation Statement, 151 Annals Internal Med. 716, 716 (2009). 230. Adrian Edwards, Communicating Risks, 327 BMJ 691–92 (2003). 739

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Reference Manual on Scientific Evidence of life and the timing of that risk whether the risk occurs now or in the future.231 Informed decisionmaking occurs when an individual understands the nature of the disease or condition being addressed; understands the clinical service and its likely consequences, including risks, limitations, benefits, alternatives, and uncertainties; has considered his or her preferences as appropriate; has participated in decision making at a personally desirable level; and either makes a decision consistent with his or her preferences and values or elects to defer a decision to a later time.232 Shared decisionmaking occurs “when a patient and his or her healthcare provider(s), in the clinical setting, both express preferences and participate in making treatment decisions.”233 To assist with shared decisionmaking, health decision aids have been devel- oped to help patients and their physicians choose among reasonable clinical options together by describing the “benefits, harms, probabilities, and scientific uncertainties.”234 In 2007, the legislature in the state of Washington became the first to establish and recognize in law a role for shared decisionmaking in informed consent.235 The bill goes on to encourage the development, certification, use, and evaluation of decision aids. The consent form provides written documentation that the consent process occurred, but the crux of the medical consent process is the discussion that occurs between a physician and a patient. The physician shares his or her medical knowledge and expertise and the patient shares his or her values (health goals) and preferences. It is an opportunity to strengthen the patient–physician relationship through shared decisionmaking, respect, and trust. V. Summary and Future Directions Having sequenced the human genome, medical research is poised for exponen- tial growth as the code for human biology (genomics) is translated into proteins (proteomics) and chemicals (metabolomics) to identify molecular pathways that lead to disease or that promote health. With advances in medical technologies in diagnosis and preventive and symptomatic treatment, the practice of medicine will be profoundly altered and redefined. For example, consider lymphoma, a blood cancer that used to be classified simply by appearance under the microscope as 231. Michael J. Barry, Health Decision Aids to Facilitate Shared Decision Making in Office Practice, 136 Annals Internal Med. 127–35 (2002). 232. Peter Briss et al., Promoting Informed Decisions About Cancer Screening in Communities and Healthcare Systems, 26 Am. J. Preventive Med. 67, 68 (2004). 233. Id. at 68. 234. Annette M. O’Connor et al., Risk Communication in Practice: The Contribution of Decision Aids, 327 BMJ 736, 736 (2003). 235. Bridget M. Kuehn, States Explore Shared Decision Making, 301 JAMA 2539–41 (2009). 740

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Reference Guide on Medical Testimony either Hodgkin’s or non-Hodgkin’s lymphoma. As science has evolved, it is now further classified by cellular markers that identify the underlying cancer cells as one of two cells that help with immunity (protecting the body from infection and cancer): T cells or B cells. Current research is attempting to characterize those cells further by identifying underlying genetic and cellular markers and pathways that may distinguish these lymphomas and provide potential therapeutic targets. The growth in the research enterprise, both basic science and clinical translational (the translation of bench research to the bedside or basic science research into novel treatments or diagnostics), has greatly expanded research capacity to generate scientific research of all types. With greatly expanded knowledge, research and specialization, judgments about admissibility and about what constitutes expertise become increasingly difficult and complex. The sifting of this research into sufficiently substantiated, competent, and reliable evidence, however, relies on the traditional scientific foundation: first, biological plausibility and prior evidence and, second, consis- tent repeated findings. The practice of medicine at its core will continue to be a physician and patient interaction with professional judgment and communication central elements of the relationship. Judgment is essential because of uncertainties in the underlying professional knowledge or because even if the evidence is cred- ible and substantiated, there may be tradeoffs in risks and benefits for testing and for treatment. Communication is critical because most decisions involve tradeoffs, in which case individual patient preferences for the outcomes that may be unique to patients and that may affect decisionmaking should be considered. In summary, medical terms shared in common by the legal and medical pro- fessions have differing meanings, for example, differential diagnosis, differential etiology, and general and specific causation. The basic concepts of diagnostic reasoning and clinical decisionmaking and the types of evidence used to make judgments as treating physicians or experts involve the same overarching theo- retical issues: (1) alternative reasoning processes; (2) weighing risks, benefits, and evidence; and (3) communicating those risks. 741

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Reference Manual on Scientific Evidence Glossary of Terms adequacy. In diagnostic verification, testing a particular diagnosis for its adequacy involves determining its ability to account for all normal and abnormal find- ings and the observed time course of the disease. attending physician. The physician responsible for the patient’s care at the hos- pital in which the patient is being treated. Bayes’ theorem (rule). A mathematical approach to integrating suspicion (pre- test probability) with additional information such as from a test result (posttest probability) by using test characteristics (sensitivity and specificity) to demon - strate how well the test performs in individuals with and without the disease. causal reasoning. For physicians, causal reasoning typically involves understand- ing how abnormalities in physiology, anatomy, genetics, or biochemistry lead to the clinical manifestations of disease. Through such reasoning, physicians develop a “causal cascade” or “chain or web of causation” linking a sequence of plausible cause-and-effect mechanisms to arrive at the pathogenesis or pathophysiology of a disease. chief complaint. The primary or main symptom that caused the patient to seek medical attention. coherency. In diagnostic verification, testing a particular diagnosis for its coher- ency involves determining the consistency of that particular diagnosis with pre- disposing risk factors, physiological mechanisms, and resulting manifestations. conditional probability. The probability or likelihood of something given that something else has occurred or is present, for example, the likelihood of dis- ease if a test is positive (posterior probability) or the likelihood of a positive test if disease is present (sensitivity). See Bayes’ theorem or rule. consulting physician. A physician, usually a specialist, asked by the patient’s attending physician to provide an opinion regarding diagnosis, testing, or treatment or to perform a procedure or intervention, for example, surgery. diagnostic test. A test ordered to confirm or exclude possible causes of a patient’s symptoms or signs (distinct from screening test). diagnostic verification. The last stage of narrowing the differential diagnosis to a final diagnosis by testing the validity of the diagnosis for its coherency, adequacy, and parsimony. differential diagnosis. A set of diseases that physicians consider as possible causes for patients presenting with a chief complaint (hypothesis generation). As additional symptoms with further patient history, signs found on physical examination, test results, or specialty physician consultations become avail- able, the likelihood of various diagnoses may change (hypothesis refinement) or new ones may be considered (hypothesis modification) until the diagnosis is nearly final (diagnostic verification). 742

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Reference Guide on Medical Testimony differential etiology. Term used by the court or witnesses to establish or refute external causation for a plaintiff’s condition. For physicians, etiology refers to cause. external causation. External causation is established by demonstrating that the cause of harm or disease originates from outside the plaintiff’s body, for example, defendant’s action or product. general causation. General causation is established by demonstrating, usually through scientific evidence, that a defendant’s action or product causes (or is capable of causing) disease. heuristics. Quick automatic “rules of thumb” or cognitive shortcuts often involving pattern recognition that facilitate rapid diagnostic and treatment decisionmaking. Although characteristic of experts, it may predispose to known cognitive errors. See Hypothetico-deductive. hypothesis generation. A limited list of potential diagnostic hypotheses in response to symptoms, signs, and lab test results. See differential diagnosis. hypothesis modification. A change in the list of diagnostic hypotheses (differ- ential diagnosis) in response to additional information, e.g., symptoms, signs, and lab test results. See differential diagnosis. hypothesis refinement. A change in the likelihood of the potential diagnostic hypotheses (differential diagnosis) in response to additional information, e.g., symptoms, signs, and lab test results. As additional information emerges, physicians evaluate those data for their consistency with the possibilities on the list and whether those data would increase or decrease the likelihood of each possibility. See differential diagnosis. hypothetico-deductive. Deliberative and analytical reasoning involving hypothesis generation, hypothesis modification, hypothesis refinement, and diagnostic verification. Typically applied for problems outside an individual’s expertise or difficult problems with atypical issues, it may avoid known cognitive errors. See Heuristics. individual causation. See specific causation. inductive reasoning. The process of arriving at a diagnosis based on symptoms, signs, and lab tests. See differential diagnosis. inferential reasoning. See inductive reasoning. overdiagnosis. Screening can lead to “pseudodisease” or “overdiagnosis,” e.g., the identification of slow-growing cancers that even if untreated would never cause symptoms or reduce survival because the screening test cannot distin- guish the abnormal-appearing cells that would become cancerous from those that would never do so. See overtreatment. overtreatment. The treatment of patients with pseudodisease whose disease would never cause symptoms or reduce survival. The treatment may place 743

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Reference Manual on Scientific Evidence patients at risk for treatment-related morbidity and possibly mortality. See overdiagnosis. parsimony. In diagnostic verification, testing a particular diagnosis for its parsi- mony involves choosing the simplest single explanation as opposed to requir- ing the simultaneous occurrence of two diseases to explain the findings. pathogenesis. See causal reasoning. pathology test. Microscopic examination of body tissue typically obtained by a biopsy or during surgery to determine if the tissue appears to be abnormal (dif- ferent than would be expected for the source of the tissue). The visual compo- nents of the abnormality are typically described (e.g., types of cells, appearance of cells, scarring, effect of stains or molecular markers that help facilitate identi- fication of the components) and, on the basis of visual pattern, the abnormality may be classified, e.g., malignancy (cancer) or dysplasia (precancerous). posttest probability. See predictive value. predictive value or posttest probability. The suspicion or probability of a disease after additional information (such as from a test) has been obtained. The predictive value positive or positive predictive value is the probability of disease in those known to have a positive test result. The predictive value negative or negative predictive value is the probability of disease in those known to have a negative test result. pretest probability. The suspicion or probability of a disease before additional information (such as from a test) is obtained. prior probability. See pretest probability. screening test. A test performed in the absence of symptoms or signs to detect disease earlier, e.g., cancer screening (distinct from diagnostic test). sensitivity. Likelihood of a positive finding (usually referring to a test result but could also be a symptom or a sign) among individuals known to have a disease (distinct from specificity). sign. An abnormal physical finding identified at the time of physical examination (distinct from symptoms). specific causation or individual causation. Established by demonstrating that a defendant’s action or product is the cause of a particular plaintiff’s disease. specificity. Likelihood of a negative finding (usually referring to a test result but could also be a symptom or a sign) among individuals who do not have a particular disease (distinct from sensitivity). syndrome. A group of symptoms, signs, and/or test results that together charac- terize a specific disease. symptom. The patient’s description of a change in function, sensation, or appear- ance (distinct from sign). 744

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Reference Guide on Medical Testimony References on Medical Testimony Lynn Bickley et al., Bates’ Guide to Physical Examination and History Taking (10th ed. 2008). Gerd Gigerenzer. Calculated Risks. How to Know When Numbers Deceive You (2002). Trisha Greenhalgh. How to Read a Paper: The Basics of Evidence-Based Medi- cine (4th ed. 2010). Gordon Guyatt et al., Users’ Guides to the Medical Literature: Essentials of Evidence-Based Clinical Practice (2d ed. 2009). Jerome P. Kassirer et al., Learning Clinical Reasoning (2d ed. 2009). Harold C. Sox et al., Medical Decision Making (2006). Sharon E. Straus et al., Evidence-Based Medicine (4th ed. 2010). 745

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