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Page 82 5 Epidemiology and Surveillance of Fetal Alcohol Syndrome The success of any public health program can be measured by comparing the incidence or prevalence of a particular societal problem before that program was implemented with its incidence or prevalence after implementation. Such data are also important for estimating the societal impact of these disorders and are crucial at the initial stages of planning, organizing, and implementing prevention programs aimed at the general population as well as at specific at-risk populations (Beauchamp, 1980). The previous chapter discusses criteria for diagnosing FAS, ARBD, and ARND. That chapter points out that diagnostic criteria serve many purposes. So, too, do epidemiology and surveillance. In addition to the important reasons outlined above, it is important to survey FAS so that children identified can receive appropriate medical care, social services, and educational interventions. Epidemiology and surveillance of fetal alcohol syndrome (FAS), alcohol-related birth defects (ARBD), and alcohol-related neurodevelopmental disorder (ARND) are ongoing but are currently hampered by inconsistent methods and criteria for gathering the appropriate data. The chapter first describes estimates of the incidence and prevalence of FAS as reported in the published literature and as measured in three main ways. The chapter then discusses methodologic issues in FAS surveillance. INCIDENCE AND PREVALENCE OF FAS, ARBD, AND ARND The literature on the epidemiology of FAS and ARBD or ARND is extensive and complicated by differences in the definition of outcomes in this evolving field. Although prospectively gathered FAS incidence rates have been published
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Page 83 in more than 20 different studies (see Abel and Sokol, 1987, 1991; Abel, in press), many of the estimates from the United States are based on high-risk populations living in lower-socioeconomic urban areas. The incidence of FAS has been estimated from data of three main types: information collected passively for another or for many purposes, such as birth defects registries; information gathered either retrospectively or prospectively from hospital or clinic-based populations, including subjects in controlled epidemiologic studies of the effects of maternal substance abuse (which frequently measure the incidence or prevalence of traits or characteristics associated with FAS, not the incidence of FAS itself); and population-based active case ascertainment. A brief review of the literature of the incidence and prevalence of FAS and other possible alcohol-related effects follows. We have attempted to map findings to current terminology (see Chapter 4). Where this was not possible, we describe the diagnostic category employed but have avoided using fetal alcohol effects (FAE) or ARBD as they had been used historically (i.e., to designate other than FAS). The sections are organized according to the general methodological approach as specified above. Registry-Based Studies The Centers for Disease Control and Prevention monitors the rate of FAS in two birth defects surveillance programs. Chavez et al. (1988) reviewed the recording of major congenital malformations in CDC's Birth Defects Monitoring Program (BDMP). Cases were identified based on hospital discharge diagnoses using codes from the International Classification of Diseases, ninth edition (ICD-9-CM; U.S. Department of Health and Human Services, 1991a). Code 760.71 is "noxious influences affecting fetus via placenta or breast milk, specifically alcohol; includes fetal alcohol syndrome." Data were collected in more than 1,500 hospitals across the United States from 1980 through 1986. The overall rate of FAS was 2.97 per 1,000 for Native Americans, 0.6 per 1,000 for African Americans, 0.09 for Caucasians, 0.08 for Hispanics, and 0.03 for Asians (Chavez et al., 1988). As might be expected, the rates of FAS ascertained from a birth certificate registry system were much lower than those for the clinic-based FAS-specific studies discussed later. The registry rate reported is about 1 per 10,000 rather than 1 to 2 per 1,000 as documented in epidemiologic studies. A subsequent CDC article on data from the BDMP estimated the overall incidence of FAS from 1979 to 1993 at 0.22 per 1,000 (CDC, 1995a). For 1992 alone, however, the rate was 0.37 per 1,000 (CDC, 1993a), and for 1993 it was 0.67 per 1,000 (CDC, 1995a); these rates are substantially higher than in previous years. According to the CDC, this increase is leading to a study to examine the sensitivity and specificity of the monitoring system. The CDC's Metropolitan Atlanta Congenital Defects Program (MACDP) is
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Page 84 a population-based registry that identifies children diagnosed with birth defects during the neonatal and infancy periods. The program monitors all births in a five-county area in and around metropolitan Atlanta. In contrast to the BDMP, the MACDP uses multiple data sources, including hospital discharge data, medical records, and birth certificates. From 1989 through 1992, the MACDP identified an overall rate of FAS of 0.23 case per 1,000 (CDC, 1995b). Other geographic regions, for example the states of California and Iowa, have birth defects registry systems. In general, the surveillance of FAS is similar in these other systems. Information on birth defects incidence and prevalence at the national level is inadequate and FAS is no exception. Birth registry systems that are used in the absence of active case identification or case-finding initiatives are not adequate approaches for producing estimates of FAS. Results are based on indicators at birth or, in the case of prevalence studies, only on indicators at a particular age. Given also that FAS is a complex diagnosis (see Chapter 4), it may go unrecognized at birth (Little et al., 1990). Thus, registry-based estimates of FAS prevalence can be expected to be gross underestimates. Clinic-Based Studies Studies that have produced rates, or estimated rates, of the incidence of FAS have been carried out in a number of countries (see Table 5-1). Many of these are based on populations seen in hospitals or clinics. These data can be collected prospectively or reviewed retrospectively. In Sweden the rate of FAS was found to be 1.7 per 1,000 births, and the rate of what seem to be ARBD and ARND 1.7 per 1,000, yielding an overall rate of 3.4 per 1,000 for diagnosable alcohol-related abnormalities (Olegard et al., 1979). Early retrospective studies in France identified 2.9 FAS children per 1,000 births (Dehaene et al., 1977) and later 1.4 per 1,000 births (Dehaene et al., 1981). More recently, Dehaene and colleagues categorized FAS and possible alcohol-related effects severity into Types I, II, and III, with Type III being the most severe effects (i.e., FAS). In monitoring 13,118 births from 1986 to 1990, Type III FAS was estimated at 1.2 per 1,000 births. Types I and II (ARBD) were estimated at 4.8 per 1,000 births. This produced a combination ARBD rate of 6.0 per 1,000 in northern France (Dehaene et al., 1991). Retrospectively gathered data invariably result in higher estimates (Abel and Sokol, 1987). For example, in contrast to these retrospective studies, prospective clinic-based studies in Australia, Canada, Finland, Switzerland, and the United Kingdom have failed to document any cases of FAS (Abel and Sokol, 1987, 1991). In the United States, incidence rates vary widely depending on study site. Hanson et al. (1978) reported an incidence rate of 1.3 FAS children per 1,000 births for Seattle, Washington. This figure represented two African-American FAS babies born in a sample of 1,529 predominately Caucasian mothers. In the
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Page 85 TABLE 5-1 Prevalence of Fetal Alcohol Syndrome (FAS), Alcohol-Related Birth Defects (ARBD), and Alcohol-Related Neurodevelopmental Disorder (ARND), and Total in Selected Previous Studies Studies Rate per 1,000 Type Study Locale FAS ARND/ARBD a Clinic based Olegard et al. (1979) Sweden 1.7 1.7 3.3 Clinic based Dehaene et al. (1977) France 2.9 Clinic based Dehaene et al. (1981) France 1.4 Clinic based Dehaene et al. (1991) France 1.2 6.0 Clinic based Hanson et al. (1978) U.S. (Seattle) 1.3 5.9 Clinic based Hingson et al. (1977) U.S. (Boston) 0.6 Clinic based Ouellette et al. (1977) U.S. (Boston) 3.1 Clinic based Sokol et al. (1980) U.S. (Cleveland) 0.6 Clinic based Sokol et al. (1986) U.S. (Cleveland) 3.0 Registry based Chavez et al. (1988) U.S. (1980-1986) Native Americans 2.9 African Americans 0.6 Caucasians 0.09 Hispanics 0.08 Asians 0.03 Registry based CDC (1993a) U.S. (1979-1992) 0.2 Registry based CDC (1993b) U.S. (1992) 0.37 Population based May et al. (1983) SW Native Americans (1969-1982) 2.0 1.1 3.1 SW Native Americans (1978-1982) 4.2 1.5 5.7 Population based Asante and Nelms-Matzke (1985) Native CanadiansBritish Columbia 25.0 Native CanadiansYukon 46.0 Population based Robinson et al. (1987) NW Canada Indians 120.0 69.0 189.0 Population based Duimstra et al. (1993) Plains Indians 3.9-8.5 NOTE: NW = northwestern; SW = southwestern. aTotal reported diagnosed or diagnosable alcohol-related birth defects include those referred to as FAS and ARBD (or FAE).
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Page 86 same study, Hanson et al. found several other infants who were born to mothers with substantial drinking histories and who had some strong FAS features. The rate of possible alcohol-related effects was then 4.6 per 1,000, yielding a total diagnosable alcohol-related abnormality rate of 5.9 for Seattle (calculated from Hanson et al., 1978). In Boston, two studies yielded FAS incidence rates ranging from 0.6 per 1,000 (Hingson et al., 1982) to 3.1 per 1,000 (Ouellette et al., 1977). In Cleveland, two studies produced estimates of FAS incidence rates ranging from 0.6 per 1,000 (Sokol et al., 1980) to 3.0 per 1,000 (Sokol et al., 1986). Other FAS studies conducted in Denver and Loma Linda found no FAS cases (Abel and Sokol, 1987; 1991). From the clinic-based studies, one can conclude that the prevalence of FAS varies by the prevalence of the problem in the select population served by the hospital or clinic and by the methodology used for case identification and ascertainment. Such studies typically result in numbers that are higher than prevalence estimates derived by using standard surveillance methodologies. Prospective Epidemiologic Studies of the Effects of Maternal Substance Abuse While the clinic-based studies described above focus primarily on the incidence of formally diagnosed cases of FAS, ARBD, or ARND, the approach that some other researchers have taken is to record maternal drinking and drug-taking patterns in large samples from clinic and hospital settings. The children of these women are then followed over time to document birth weight, length, head circumference, structural malformations, and other relevant traits. Few, if any, of the offspring of these women have FAS, because so relatively few of the women who would enroll in such a study abuse alcohol at levels that cause FAS. Most of the women in these studies who drink do so in the light to moderate ranges. The problems of interpretation and the implications of these data are discussed in detail in Chapter 8. Following children longitudinally provides important information that can support our understanding of the range of alcohol teratogenesis. Day et al. (1989, 1990, 1991) published the results of measuring offspring traits at birth, 8 months, and 3 years of age. In these studies, carried out in Pittsburgh, low birth weight, decreased head circumference and length, two or more minor anomalies, and significantly slower growth were found to be present in the children of mothers who consumed an average daily alcohol volume of one or more drinks during pregnancy (Day et al., 1991). Similar findings came from the Cleveland, Seattle, and Detroit longitudinal studies. These trait studies are important for several reasons. They document a wider range of fetal alcohol damage than FAS alone, and they focus on more singular, individual, and quantifiable traits in the children, which also creates an advantage in sample size. Further, the longitudinal ascertainment of maternal traits (e.g.,
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Page 87 drinking patterns and health status), and offspring signs of fetal alcohol exposure in a wider population has considerable utility, because some traits (e.g., hyperactivity) may not emerge until several years after birth. The range of outcomes studied and the longitudinal approach can provide valuable information in planning and evaluating comprehensive programs of prevention, because they both broaden the target of prevention (all levels of alcohol-related effects) and provide a greater range of dependent variables to use as outcome measures. This approach is discussed in more detail later in this chapter. The relation between the incidence of FAS and the incidence of these traits associated with prenatal alcohol exposure is not fully understood. Population-Based Epidemiology Studies Population-based epidemiologic studies using active case ascertainment can assist in addressing some of the criticisms mentioned above, can provide relevant information on the magnitude of the problem in specific communities, and may be more useful for comprehensive community-based prevention efforts. The four major population-based studies done in the world to date were all carried out almost exclusively in Native American communities in North America. In these population-based studies, active and extensive community outreach is carried out for case finding, and all children in a particular population are screened for any physical features (e.g., dysmorphology or low birth weight), family history, or other background characteristics that might make them candidates for the diagnosis of FAS or ARBD. Using a population-based outreach network in northwestern Canada, Asante and Nelms-Matzke (1985) estimated the rate of FAS and possible alcohol-related effects at 46 per 1,000 Native Canadian children in the Yukon and 25 per 1,000 in British Columbia. Furthermore, these authors estimated that 51 to 66 percent of all children in special education with learning disorders in the study regions were exposed to alcohol in utero. Robinson et al. (1987) screened all children less than 19 years of age in a small Native Canadian community noted for its high rates of alcohol consumption. Twenty-two children born to women who used alcohol during pregnancy and were diagnosed with FAS, or what the committee terms partial FAS, were identified, yielding a prevalence of 190 FAS or partial FAS cases per 1,000 children. This is the highest prevalence rate ever recorded anywhere. Interestingly, these 22 children were produced by 14 mothers (fewer than one-third of the mothers in this heavy-drinking community), and in 46 percent of the total pregnancies the mothers were abstainers. Of the verified drinking pregnancies, 40.7 percent of the children were diagnosed as FAS or partial FAS. In another population-based prevalence study carried out in seven different Native American communities in the southwestern United States by May and colleagues (May and Hymbaugh 1983; May et al., 1983), 115 children were
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Page 88 found to have FAS or traits reminiscent of FAS but less severe. The prevalence of FAS or these less complete cases was highly variable among the three different tribal cultural groups involved in the study. The prevalence of FAS among children 0-14 years was 1.6 per 1,000 for Navajo Indians, 2.2 for Pueblo Indians, and 10.7 for two groups of southwestern Native Americans. Overall, the weighted average rate for southwestern Native Americans was 2.0 per 1,000 for FAS and 3.1 per 1,000 for FAS and the less severe manifestations combined. In the most recent birth cohort studied, however, the FAS rate was higher, 4.2 per 1,000 for FAS and 5.7 for FAS and the other manifestations combined. Of more importance for prevention, however, is the fact that a number of maternal and social risk factors were determined in this study. These findings are presented below. In a study of four North and South Dakota Plains Indian reservations, Duimstra et al. (1993) used low birth weight and a developmental screening test in an outreach, case-finding network to assess the prevalence of FAS. The rate of FAS confirmed by dysmorphology exam was 3.9 per 1,000. When the rate of confirmed cases was projected to all children identified as suspected cases by the outreach network, necessitated by cases lost to follow-up, the estimated rate of FAS rose to 8.5 per 1,000. The overall significance of these population-based studies is that they may provide more accurate prevalence data and could point the way to more valuable information for comprehensive prevention programs. By not looking only at the prevalence and characteristics of FAS, ARBD, and ARND as presented in various clinics, population-based studies possess the capability of examining a range of social and cultural influences that impact upon the rate of these conditions. Such conditions may be readily amenable to the design of large-scale or intensive preventive efforts. For example, the rate of maternal risk and the characteristics of the social milieu could help define adequate approaches and targets for prevention and the magnitude of effort required. In addition, the programs of awareness and emphasis on intensive and societal-based efforts of case identification are advantages of population-based approaches. FAS needs such an approach if its prevalence is to be accurately estimated. In the Native American tribes highlighted in the FAS prevalence studies, the drinking pattern is bimodal: a high proportion of the tribe does not drink at all, but among those who do drink there is a high proportion of heavy and abusive drinkers (May, 1994). Many of those young and middle-aged adults who drink do so in large quantities and generally participate in subcultures emphasizing long binges of heavy drinking leading to very high blood alcohol levels over several days. Because many reservations prohibit the sale and possession of alcohol, drinking is pursued outside the mainstream, normal social activities and law, generally in border town communities away from the reservation and its traditional culture and sanctions. Social isolation and the entrenchment of heavy-drinking behavior among some females, through stigmatization, is common in some tribes. This often leads to a high frequency of FAS, ARBD, and ARND
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Page 89 births in some tribes and subcultures within them (May et al., 1983). Alcohol is, by far, the major drug of choice among virtually all Native Americans and tribes, with only occasional use of marijuana, inhalants, or solvents among some problem drinkers (see May, 1994). Issues and Considerations It appears, as documented above, that the literature on the prevalence and epidemiology of FAS is far from consistent or conclusive. Various studies reporting the occurrence of FAS range from 0.6 to 3 births per 1,000 in most populations, with some communities having much higher rates. Rates in inner cities, for example, are 2.29 per 1,000 versus 0.26 at sites where the population is middle class (Abel, in press). FAS and other diagnosable ARBD or ARND designations may occur on average in as many as 6 per 1,000 births (May et al., 1983). Because only a proportion of mothers who are very heavy drinkers will have children with FAS (Abel, in press), it is vital that researchers do more to study and compare the social and biological characteristics of FAS mothers with those especially heavy drinkers who do not have FAS children. The consistency and, hence, comparability of the FAS prevalence (and overall epidemiologic) methodology need to be improved. Increased understanding of the maternal characteristics and social variables that influence FAS, ARBD, and ARND is also needed. Other review articles on FAS have raised key issues regarding most of the epidemiologic studies on possible alcohol-related effects (Abel, in press; Abel and Hannigan, in press; Abel and Sokol, 1987, 1991; Russell, 1991). These key issues include methodologies and definitions in case finding and diagnosis; wide variation in the types of populations studied; consistency of data gathered by prospective versus retrospective methods; and improvements in surveillance techniques. In general, it remains difficult to reconcile incidence and prevalence rates between studies. Role of Epidemiology in Prevention Programs The major public health planning document of this decade, Healthy People 2000, states that the baseline incidence rate for FAS for the United States is 0.22 per 1,000 births (U.S. Department of Health and Human Services, 1991b). Furthermore, the goal for the year 2000 is to reduce this figure to 0.12. This goal as an absolute number may be unrealistic given the obvious variances in the incidence and prevalence rates for FAS summarized in Table 5-1 and in the three composite estimates by Abel (in press) and Abel and Sokol (1987, 1991), which indicate worldwide variability of rates ranging from 0.33 per 1,000 to 0.97 per 1,000 (Abel, in press). The latest estimate for the United States is 1.95, far greater than the Healthy People 2000 baseline rate of 0.22 per 1,000 (Abel, in
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Page 90 press). Many Healthy People 2000 goals were expressed as a percentage of the baseline and some of those baselines were revisited and changed. A goal of 50 percent reduction, which is what the FAS goal approximates if compared to the baseline of 0.22 per 1,0000, seems more reasonable, but only if the baseline is adjusted to more accurately reflect the consensus of the field. As this chapter illustrates, however, there is no consensus about the incidence of FAS except that it is much higher than the Healthy People 2000 baseline rate. Exactly how much higher is not clear. As long as we do not have consistent methods, criteria for assessment, or sufficient understanding of FAS prevalence, targeted prevention goals will be difficult to monitor. Consistent Diagnosis FAS may not be well recognized or routinely and consistently documented by many physicians. In one study in Texas, Little et al. (1990) found that the diagnosis of FAS was not made in the medical records of any of the 40 infants born to 38 women who had at least four alcoholic beverages per day. The charts of six of the infants included notations of features of FAS. In follow-up of these offspring, 17 had very poor growth and development records and other possible indicators of FAS, ARBD, or ARND. Conversely, in other locales FAS may be over diagnosed (Aase, 1994; Abel and Sokol, 1987). In some ethnic minority communities, and communities perceived as having alcohol abuse problems, individuals may be more likely to receive the diagnosis when specific case evidence is marginal (Aase, 1994; Chavez et al., 1988). Chavez et al. (1988) raised several important issues pertaining to differences in prevalence results with respect to ethnicity. They suggested that (1) physicians tend to be more likely to look for particular malformations among particular ethnic groups; (2) minority status may elevate the rates of reporting particular malformations; (3) hospitals participating in the birth defect monitoring program(s) may not be representative of all hospitals; (4) socioeconomic factors cannot be ruled out as important contributions to the burden of ARBD malformations; and (5) many of the malformations may have been associated with genetic and environmental factors. Each of these issues is relevant for both FAS epidemiology studies and comprehensive prevention programs. Use of Multiple Data Sources Several recent projects of surveillance and prevalence assessment have utilized multiple data sources and approaches. In Alaska, multiple secondary data sources were used to estimate statewide and ethnic-specific prevalence (Centers for Disease Control, 1993b; Egeland et al., submitted for publication). By using ICD-9 codes; private sector data sources (inpatient and outpatient); education, genetics, and disability program records; and Alaska Native Health Service
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Page 91 records, case definitions were used to estimate FAS prevalence and some descriptive epidemiologic characteristics of FAS children and their mothers. As one would expect, results proved to be similar in many ways to various findings from the other methodologies used as described previously. However, by combining several data sources and using a more active case-finding effort, estimates of prevalence may have been more accurate. In addition, using a combination of active and passive surveillance systems indicated a high FAS prevalence rate among Alaska Natives than by an active screening and referral effort alone. SURVEILLANCE METHODS FOR FETAL ALCOHOL SYNDROME On a national level, there are two ways to monitor the impact on public health of alcohol use during pregnancy by using surveillance strategies. The two surveillance approaches discussed in this section involve passive and active methodologies. The advantages and disadvantages of each approach are presented here, along with possible solutions to the problems they pose with respect to FAS. Given the stated goal of reducing FAS, much more attention has to be paid to standardization of data collection, whatever the strategy for assessment. Passive Surveillance Passive surveillance is the strategy generally used to monitor birth defects (Lynberg and Edmonds, 1992). This strategy simply tallies the number of cases of a defined birth defect or syndrome noted on existing documents, such as medical records, and relates that figure to some population. Review of individual cases is not done. This is the strategy behind the CDC's Birth Defects Monitoring Program, discussed previously, which used hospital discharge data on both live and stillborn newborns to estimate the incidence of FAS at 2 cases per 10,000 between 1979 and 1992, and 3.7 per 10,000 births in 1992 (CDC, 1993a). Advantages and Disadvantages The advantage of passive surveillance for FAS is that it is directly comparable with the methodologies used to assess the incidence of other birth defects, allowing a comparison of relative rates. It allows monitoring of secular changes and differences by geographic distribution or sociodemographic status, as well as comparison of the distributions of different kinds of birth defects. There are several disadvantages to this methodology, however, for the surveillance of FAS. A major problem is the accuracy with which FAS is diagnosed, particularly at birth. This inaccuracy is due to several factors: (1) it is difficult to evaluate central nervous system (CNS) status at birth; (2) many clinicians are not trained to identify FAS; (3) inconsistent criteria are used for case definition; and
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Page 92 (4) clinicians may be reluctant to identify alcohol problems or to label women as having alcohol problems. Clinicians continue to use, somewhat idiosyncratically, a diverse pattern of traits to diagnose FAS (Clarren and Astley, 1994). There may also be ''selective" case finding by physicians who look for particular malformations among some minority groups compared with others (Chavez et al., 1988). Case finding of pregnant substance abusers similarly focuses on women with certain characteristics (e.g., a history of alcohol or drug use noted in their charts, older age, African-American ethnicity, use of tobacco, a history of social or emotional problems). In the absence of these markers, few pregnant women are screened for alcohol or drug use, and about 50 percent of all relevant cases may be missed by clinic staff (Reynolds and Day, unpublished data). A similar problem may likewise affect detection of FAS. In addition, the characteristics that are prominent in FAS and used for diagnosis may differ by age. A survey reported by Clarren and Astley (1994) demonstrated that while clinicians consider microcephaly and growth retardation to be important parameters in newborns and infants, in older children they are more likely to consider microcephaly in conjunction with behavioral problems as pathognomonic. A solution would be to use the standardized criteria for diagnosis presented in Chapter 4 of this report. Possible Solutions Passive surveillance as used currently can be improved for FAS surveillance. Improvements could be made directly by improving passive surveillance of FAS or indirectly by using proxy indicators of FAS. Direct Measures Clinicians can be educated to better recognize FAS. However, it is still likely that biased reporting will continue to occur, given the negative labeling associated with alcohol involvement. It may be difficult to determine accurately the incidence of FAS at birth, particularly in environments where clinicians are not well trained, not sensitive to or willing to report the use of alcohol among pregnant women, or not willing to use standardized diagnostic criteria. Providing a confidential reporting mechanism, separate from the medical record or birth certificate, would reduce this bias. Even in the presence of these improvements, however, correct ascertainment of the rate of FAS at birth remains problematic due to the difficulty in assessing CNS or neurobehavioral abnormalities at this age. Indirect Indicators An alternative to monitoring the incidence of FAS at birth is to develop surveillance criteria that would identify a group of newborns with a high probability of having FAS, for example, newborns with birth weights below 2 standard deviations for gestational age. Criteria such as birth weight that are
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Page 93 TABLE 5-2 Predictability of Fetal Alcohol Syndrome Based on Surveillance Criteria Head Circumference <10th Percentile and One Facial Anomaly (N = 29) All Remaining Subjects (N = 713) Average daily volume (ADV), first trimester 1.37 0.57 ADV third trimester 1.28 0.10 IQ score at age 6 85.5 95.9 Weight at age 6 (kg) 20.9 23.2 Height at age 6 (cm) 113.8 119.5 Head circumference at age 6 (mm) 513.4 521.2 NOTE: All comparisons are significant at P < 0.001. SOURCE: Reynolds and Day, unpublished data. routinely recognized, measured, and noted in the medical record are not subject to clinical judgment. This strategy was adopted in a study of four American Indian communities where the investigators selected a group of children who had a birth weight of less than 3,000 grams. These children were referred for evaluation for FAS if they had poor performance on a developmental screening test or if they had a head circumference below the 10th percentile; 4 out of 24 suspected cases were confirmed as FAS (Duimstra et al., 1993). An example of data analyzed for indirect or proxy indicators of FAS is presented in Table 5-2. The data in this table are from the Maternal Health Practices and Child Development Project, an ongoing assessment of the long-term effects of substance use during pregnancy. This is a prospective epidemiologic study of pregnancy outcomes, and one of few that have followed a cohort from early pregnancy up to the child's tenth year. The women selected for this study represent the entire spectrum of alcohol use, although the majority were moderate drinkers and moderate users of other substances. They were interviewed for alcohol use in their fourth and seventh prenatal months, and their offspring were assessed at delivery, 8 and 18 months, and 3 and 6 years of age. The cohort used for analysis was 742 mother-child dyads. Although these data were collected as part of a controlled, prospective epidemiologic study, the data used in the example are representative of data that could be gathered passively for a surveillance effort. Surveillance criteria for proxy indicators of FAS were defined as either head circumference, weight or height at birth less than the 10th percentile, and the presence of at least one facial anomaly. The facial anomalies were selected from the list of facial dysmorphic features that are part of FAS. Children who had a growth deficit at birth, defined as weight or height or
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Page 94 head circumference below the 10th percentile, combined with the presence of at least one facial anomaly, were significantly more likely to have been exposed to alcohol prenatally; had significantly lower weight, height, and head circumference at three and six years; and scored significantly lower on the composite score of the Stanford-Binet Intelligence Scale. It was not possible, in this moderately exposed population, to estimate the incidence of FAS, but the strategy may lend itself to such estimates if the sample size is large enough. To establish a relationship between the incidence of cases with the surveillance criteria and the occurrence of FAS, however, would require replicated investigations using dysmorphologists trained in the identification of FAS and follow-up of these research cohorts over the first few years to determine the predictability of the surveillance criteria to the diagnosis. The advantages of a surveillance program using indirect measures or indicators lie primarily in three areas: (1) lower cost, because the criteria are already ascertained and noted in the birth or other record; (2) more accurate measurement of the criteria; and (3) elimination of the problem of negative labeling of women by clinicians. The disadvantages of this method lie in the general problem of extrapolating from the surveillance criteria to the incidence of FAS and include pervasive problems pertaining to the diagnostic abilities of clinicians. In addition, a decrease in the prevalence of the indirect marker would not necessarily reflect a proportionate decrease in the prevalence of FAS. In passive surveillancewhether direct or indirect measurement is usedit is important to monitor multiple sources for the detection of cases (e.g., birth and death certificates, Medicaid claims, private pediatric practice case files) because no one source can identify more than a minority of cases (CDC, 1993b). Active Surveillance for Fetal Alcohol Syndrome Active surveillance implies direct collection and review of cases using well-defined protocols rather than using data such as medical charts (Lynberg and Edmonds, 1992). Medical charts can be used as source for potential cases, but these cases are reviewed for the purposes of the surveillance effort. The hallmark of these kinds of protocols for FAS is the prospective epidemiologic study of the effects of maternal substance abuse. In this study every case is followed from a predetermined entry point (time A) to a specifically defined end point (time B; e.g., birth). There have been few examples of active surveillance outside the focused research literature. Most of these studies have had small sample sizes; they are far from representative; and the diagnostic criteria are not consistent (see clinic-based studies in Table 5-1). In general, the rates of FAS are higher by an order of magnitude than those estimated from passive surveillance studies (Abel, in press; Abel and Sokol, 1987, 1991; May, in press).
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Page 95 Advantages and Disadvantages As illustrated above, a comparison of the incidence rates generated by active and passive surveillance demonstrates that active surveillance detects substantially more cases (Klaucke, 1992; May, in press). Moreover, control over data collection also implies control over data quality. Thus, the diagnoses are more likely to be valid and reliable. Because of this, direct and more accurate measurement of the rate of FAS is possible using active surveillance. Population-based active surveillance programs can be tailored to characteristics of the population under study and can be linked more closely with prevention efforts. The disadvantages of active surveillance are threefold: (1) it is very expensive to collect data from a population large enough to yield representative rates; (2) it is extremely labor intensive; and (3) it is selective, in that only subjects who appear at entry will be assessed. One report noted a tenfold difference in costs between active and passive surveillance (Klaucke, 1992). The large epidemiologic studies that actively studied effects of maternal alcohol abuse were usually centered in large cities and within academic and research facilities. Other more active surveillance programs for FAS occurred in select populations. As a result, the data are likely to be biased and cannot be extrapolated to the general population. Few cases of FAS were identified in the major prospective epidemiologic studies of maternal substance abuse in major U.S. cities (e.g., Seattle, Pittsburgh), because the alcohol exposure generally was low to moderate. The Atlanta study included many women who drank heavily, and many dysmorphic children were identified. Proxy Measures in an Active Surveillance Program Just as passive surveillance can be refined by using or including indirect measures that focus on birth weight or some other indicator for case finding, so too can active surveillance for FAS include proxy measures. The approach to proxy measures suggested for passive surveillance could be used, if validated, for active surveillance of FAS. Population-based studies in representative populations could help determine the best proxy measures for an active surveillance program. Alternatively, prevalence of alcohol abuse can be used indirectly to measure or at least approximate the risk of FAS and the success of prevention efforts. This is because FAS has a known causealcohol abuse. Alcohol Abuse Because FAS, by definition, occurs only among offspring of women who abuse alcohol, a logical point for screening would be alcohol abuse. A screen for alcohol abuse would yield a low rate of cases but would identify women who are at high risk of having a baby with FAS, ARBD, or ARND. This type of screening has two advantages: (1) it identifies the population that is at the
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Page 96 highest risk of having a child with FAS, and (2) it identifies a population that is unquestionably in need of intervention. The disadvantages of this approach, however, are numerous: (1) the diagnosis of alcohol abuse is often unreliable, (2) the diagnosis of alcohol abuse is often avoided by clinicians to preclude labeling women, and (3) women may not report symptoms of alcohol abuse. The availability of a biomarker of alcohol exposure could be useful, but none currently exists that could be used in a surveillance program (see Chapter 7). The rate of FAS among the offspring of women who abuse alcohol is not known; the few estimates available are relatively low (Abel, in press; Abel and Sokol, 1987), and the estimates show a varying rate by birth order (Abel, 1988). Thus, prescreening for alcohol abuse to estimate FAS is problematic. Drinking Practices Similar problems can be seen when we consider measuring drinking or heavy drinking during pregnancy, although this is an attractive option, given the opportunities it would present for prevention and intervention. However, measuring drinking or heavy drinking is time intensive and remains an effort that few clinicians are trained or willing to make. Drinking, particularly heavy drinking during pregnancy, is a stigmatized behavior; it is likely to be underreported by women and reported in a biased fashion by clinicians. Moreover, we do not know how "heavy" heavy drinking must be to result in FAS, ARBD, or ARND and we may never be able to arrive at a consensus because of the numerous other social, personal, and biological factors that interact with alcohol consumption to produce FAS, ARBD, and ARND (Abel and Hannigan, in press). Feasibility of Surveillance Surveillance of FAS can be accomplished by actively seeking or ascertaining cases of FAS or by establishing surveillance criteria for proxy indicators of FAS and actively ascertaining the incidence or prevalence of cases that meet those criteria. Some suggestions for doing this have been described above. Given the limitations of passive surveillance for FAS, it is possibly more efficient to actively ascertain the incidence or prevalence of cases that meet surveillance criteria for proxy indications and then estimate the rate of FAS. This would require research to validate the criteria, to establish the accuracy of their measurement and reporting, and to determine an appropriate estimation (or "conversion") factor. Population-based epidemiologic studies can be very useful as part of an active surveillance effort. Given the inadequacy of passive surveillance for estimating the magnitude nationally of the FAS problem, for indicating success or failure of prevention efforts, and for identifying FAS children and families in need of clinical, social, and educational services, other approaches need to considered, expanded, and validated.
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Page 97 CONCLUSIONS AND RECOMMENDATIONS The committee concludes that FAS, ARND, and ARBD are a completely preventable set of birth defects and neurodevelopmental abnormalities and that FAS is arguably the most common known nongenetic cause of mental retardation. Further, ARND and ARBD are reported to occur even more frequently than FAS. Thus, the results of heavy prenatal alcohol exposure constitute a major public health concern. The committee endorses the efforts of the Centers for Disease Control and Prevention to move away from passive surveillance methods, which have been unsuccessful in defining the magnitude of this problem, but recognizes that no national baseline is available to judge the impact of public health and other preventive interventions. The committee encourages CDC's new efforts to implement active surveillance strategies in state- and university-based surveys. However, to address the lack of baseline data and the wide variation of prevalence estimates for subpopulations, including ethnic minorities, the committee recommends that • an interagency plan be developed for a national survey to estimate the prevalence and incidence of FAS, ARND, and ARBD, which could utilize active surveillance techniques (direct or indirect); • prevalence surveys of FAS, ARND, and ARBD be repeated at periodic intervals; • data on prevalence of FAS, ARND, and ARBD be integrated with data on the drinking behavior of pregnant women to improve risk assessment for these disorders; • improved data collection and surveillance be implemented to identify specifically children with FAS, ARND, and ARBD in various social and educational environments (e.g., maternal and child health block grant programs, Head Start programs, and Early Intervention and Special Education Services); and • when active surveillance strategies are employed that identify children with FAS, ARND, or ARBD, appropriate linkages should be in place among agencies and local clinics to facilitate treatment. REFERENCES Aase JM. Clinical recognition of FAS: Difficulties of detection and diagnosis. Alcohol Health & Research World 1994; 18:5-9. Abel EL. Commentary: Fetal alcohol syndrome in families. Neurotoxicology and Teratology 1988; 10:12. Abel EL. An update on incidence of FAS: FAS is not an equal opportunity birth defect. Neurotoxicology and Teratology, in press. Abel EL, Hannigan JH. Maternal risk factors in fetal alcohol syndrome: Provocative and permissive influences. Neurotoxicology and Teratology, in press.
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Representative terms from entire chapter: