Complementary and Alternative Medicine in the United States (2005) / Chapter Skim
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3 Contemporary Approaches to Evidence of Treatment Effectiveness: A Context for CAM Research
3 Contemporary Approaches to Evidence of Treatment Effectiveness: A Context for CAM Research
Pages 74-107
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From page 74... ...
A BRIEF ACCOUNT OF THE DEVELOPMENT OF TREATMENT EFFECTIVENESS RESEARCH As noted in Chapter 1, over the past twenty years practitioners of conventional medicine have made a marked shift from a reliance on experience (directly observed or as recorded by others in medical journals) to a reliance on more rigorous research to evaluate the effectiveness of treatments.
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From page 75... ...
. At the time, few of the procedures in question had been subjected to randomized controlled clinical trials or other credible clinical studies.
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From page 76... ...
Professional organizations such as the American College of Physicians instituted rigorous guideline development processes, increasing recognition of the severe limitations of the evidence base for the treatment of common conditions. Evidence of Effectiveness for Prescription Drugs The limited evidence base for surgery and other procedures for the common conditions targeted by outcomes research contrasted sharply with the richer body of evidence for medical therapies.
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From page 77... ...
rapidly built the capacity to conduct those clinical trials necessary to meet the standards set by FDA. More Recent Developments: Evidence-Based Medicine As the need for evidence became more evident and funding for clinical research became more available, many academic settings emphasized development and use of methods for gathering clinical evidence.
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From page 78... ...
Because not all treatments have been subjected to formal study and because some treatments cannot be studied without investment in massive clinical trials, it will not be possible to base all treatment decisions on published evidence. Nevertheless, the concept of evidence-based medicine asks that decisions be based on published scientific evidence when it is available and that investments be made to gather evidence in as many areas of medical care as possible.
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From page 79... ...
The next section examines a variety of research methods available for use in conducting clinical effectiveness research. BASIC FEATURES OF CONTEMPORARY CLINICAL EFFECTIVENESS RESEARCH A Taxonomy of Clinical Research Methods Many factors can influence the outcome of treatment.
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From page 80... ...
Observational studies have many advantages. They are much less costly than randomized trials, they can have huge study populations, and the results are more likely to represent practice (Benson and Hartz, 2000)
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From page 81... ...
For example, a researcher might study pain and disability levels as outcomes in a cohort of patients older than 70 years of age who received lumbar fusion surgery for severe sciatica. The distinguishing feature of cohort studies is that researchers gather data on treatment and possible confounders at one point in time and measure outcomes at a later point in time.
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From page 82... ...
Case-Control Studies. The study population in a case-control study in the domain of treatment effectiveness consists of the cases (those with the target outcome, such as complete pain relief)
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From page 83... ...
They are a relatively powerful method for the testing of hypotheses because repeating a measurement many times (or even once) for an individual reduces statistical variation and narrows confidence intervals.
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From page 84... ...
and some additional measurement work may be required for these modalities; but in principle, virtually any subjective experience can be captured either as present or absent or as present as a matter of degree. Because subjective experiences cannot be independently validated, and because they can be significantly affected by context, contrast, and expectation effects, it is particularly important to try to build in features of the study design that minimize these kinds of biases.
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From page 85... ...
Doing these two things minimizes the opportunity for any systematic bias either for or against a particular treatment being studied. To the extent that treatments involving CAM are designed to influence objective endpoints like survival, blood pressure, tumor size, or the alignment and spacing of vertebrae, standard measures of these endpoints, with appropriate blinding and other controls for bias, should be suitable for treatment effectiveness research in CAM.
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From page 86... ...
One form of a multivariable model would include all of the predictor variables and might show that several predictor variables were significant predictors of the end-of-study blood pressure. One of them would be Drug A and another might be salt intake.
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From page 87... ...
One can compare two antihypertensive drugs by their effects on blood pressure; or one can compare their effects by determining the rates of strokes, congestive heart failure, or myocardial infarction between the two groups of patients taking the two drugs. Blood pressure is an intermediate outcome, of interest mostly because it predicts outcomes that frighten patients, such
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From page 88... ...
Once several studies show, however, that lower blood pressure predicts fewer strokes, the decision to pay for a new antihypertensive drug might well rest on its effect on blood pressure, with the implicit assumption that the lower blood pressures brought about by treatment with the new drug relative to those achieved with standard therapy imply that the patients will experience fewer strokes. Therefore, although distal outcomes mean more to patients, it may not be necessary to measure them to determine whether a new drug is equal to or better than the standard therapy.
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From page 89... ...
A QALY is a year living in a specific state of health relative to the most desirable health state, usually perfect health. The relationship between a desirable health state and a less desirable one is a number, called a utility, which expresses the ratio of the patient's preference for a specific health state compared with that for perfect health.
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From page 90... ...
If the study population is small, the outcomes are more likely to differ by chance from the outcomes that would occur in the universe from which the sample was drawn. Because the results from any one sample can be atypical, scientists use the concept of the 95 percent confidence interval, which is the range of outcomes that would occur in 95 of 100 samples from the universe.
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From page 91... ...
If it includes 0, the interaction term is not a statistically significant predictor of the dependent variable (e.g., Drug A, salt intake, and end-of-study blood pressure, as in the earlier example)
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From page 92... ...
Effectiveness Studies Effectiveness studies evaluate the technology under real-world conditions of actual medical practice. The study population resembles that which one would see in day-to-day clinical practice, which means that any results are likely to apply to real-world clinical practice.
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From page 93... ...
So, the researchers allow the doctors caring for the patients to use medications in addition to the study medications to get a patient's blood pressure to a target level. The other blood pressure medications are "cointerventions." Cointerventions can be confounders if they affect the outcome state, which is heart failure in this example.
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From page 94... ...
The use of an appropriate statistical design can account for the effects of clustering, so that the statistical power of the study and the widths of resulting confidence intervals are accurately known. Widening of the 95 percent confidence interval after this statistical adjustment is made means that clustering of outcomes is present.
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From page 95... ...
Note that it does not use a hierarchy of study designs ranging from the most powerful (randomized clinical trials) to the weakest (case series)
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From page 96... ...
Preventive Services Task Force hierarchy, this hierarchy depends on the study design, the number of studies in the body of evidence, and the consistency of study results. In this hierarchy, the combined results of several randomized controlled clinical trials (RCTs)
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From page 97... ...
· Level 2b evidence -- A single-cohort study · Includes randomized clinical trial with >20 percent drop-outs · Level 2c evidence -- Ecological studies (performed with a preexisting dataset) · Level 3a evidence -- Systematic review of many case-control studies (with homogeneity)
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From page 98... ...
create problems in generalizing findings to routine practice settings. · Other study designs, including observational studies or "effectiveness RCTs," may provide evidence that is at least equally compelling as that provided by an "efficacy RCT." Effect size is another consideration that must be taken into account along with features of study design when one weighs the strength of evidence for a particular therapy.
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From page 99... ...
These criteria typically include · Features of the study design that allow strong inferences to be made about cause-and-effect relationships:
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From page 100... ...
A single study is rarely definitive, although some large, well-designed clinical trials may produce evidence that is treated by the scientific community as definitive. Confidence in the existence of cause-and-effect relationships grows with the ability to see them in multiple studies over time.
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From page 101... ...
There is often a gap in time between the publication of scientific evidence of the effectiveness of a new treatment and the widespread adoption of that treatment by most or all members of a professional community, along with some appropriate caution and skepticism about new findings that seem to run counter to daily experience. Teachers train students in what the members of the professional community typically do on a daily basis as well as what the published literature says that they could or should do.
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From page 102... ...
Even when all other criteria have been met, a new treatment may not be adopted if the provision of it will not be adequately reimbursed. · The extent to which the patient population is similar to those studied in clinical trials or other studies of treatment effectiveness.
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From page 103... ...
Questions about the applicability of clinical research methods to CAM are described and discussed below. Emphasis on Efficacy Rather Than Effectiveness As noted above, the distinction between efficacy and effectiveness refers to the extent to which a treatment has a measurable positive effect in highly controlled clinical trial contexts (efficacy)
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From page 104... ...
In addition to the problem of organizing RCTs for widely used treatments, there may also be a problem with all other study designs that involve some form of control condition that involves administration of a possibly ineffective treatment. Relatively Long Delay from First Development of a Treatment to Assembly of Large Body of Evidence The FDA has requirements for research on new drugs before they can be prescribed, but there are no similar requirements for surgical procedures and most CAM modalities.
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From page 105... ...
This approach to identifying effective treatments is fundamentally different from the approach that emphasizes individual tailoring of treatments found in CAM modalities like homeopathy or traditional Chinese medicine. The desire to have objective, well-defined study endpoints in RCTs can lead to a focus on health outcomes like mortality, tumor shrinkage, or change in a measurable physiological parameter like temperature or blood pressure.
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From page 106... ...
2000. Complementary and alternative medicine use among elderly persons: One-year analysis of a Blue Shield Medicare supplement.
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From page 107... ...
U.S. Preventive Services Task Force.
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