AIDS, Sexual Behavior, and Intravenous Drug Use (1989) / Chapter Skim
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1 Monitoring the Epidemic's Course
1 Monitoring the Epidemic's Course
Pages 31-72
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From page 31... ...
For example, most of the aclults who will be 1In this chapter, we focus on HIV and AIDS statistics. In Chapter 2, we discuss the potential value of reliable statistics on other sexually transmitted diseases that should (other things being equal)
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From page 32... ...
is presumed to be due to the fatal consequences of HIV infection in cases that did not meet the surveillance definition for AIDS. Increases in non-AIDS deaths among New York City IV drug users between 1981 and 1985 occurred in the following HIV-related categories: pneumonia (not Pneumocystis carinii)
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From page 33... ...
in the interpretation of the AIDS case data.4 PREVALENCE AND INCIDENCE OF HIV INFECTION Prevalence denotes that proportion of a population that is currently infected; it is usually expressed as cases per 1,000 or per 10,000, or it may be written as a percentage (e.g., 0.4 percent, or 4 cases per 1,000~. Incidence denotes the rate of occurrence of new cases of infection per unit of time (e.g., per year)
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Uses of HIV Prevalence and Incidence Data There are three important uses for reliable HIV prevalence and incidence data. First, such ciata can be used to compare population groups in terms of current HIV prevalence and, subsequently, to target prevention services to those groups that are most in need.
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Estimates of HIV prevalence among blood donors, however, were an order of magnitude lower 1 to 3 per 10,000. Despite the large number of persons screened in the four testing programs shown in Table 1-1, the results are not representative of the population.
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Monitoring Trends It is sometimes asserted that, although available HIV prevalence data are biased, they may be sufficient for following trends. Yet there are good reasons to be skeptical of this assertion.
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Variation in Estimated HIV Prevalence for Selected Groups The CDC report noted substantial differences in the estimated prevalence of HIV infection on the basis of the following: . "risk factors" homosexual sex among men, IV drug use, hemophilia, or heterosexual sex with persons at risk; .
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From page 38... ...
Furthermore, the reported variations in HIV prevalence often mirrored differences in the number of reported AIDS cases, suggesting that the estimates may be sufficiently accurate to provide a crude ranking of various groups in terms of HIV prevalence. Major groups for whom HTV prevalence and incidence data are presented in the CDC report include homosexual and bisexual men, {V drug users, hemophiliacs, -heterosexual partners of HTV-infected persons (or persons in recognized risk groups)
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From page 39... ...
There are indications, however, that the likelihood of infection in a given sample will be correlated with the type and severity of coagulation disorder: reported HIV prevalence rates were 70 percent for hemophilia A and 35 percent for hemophilia B Heterosexual Partners of Persons with HIV Infection or at Recognized Risk.
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From page 40... ...
HIV prevalence among female prostitutes ranged from O to 45 percent, with the highest rates in large inner-city areas in which drug use is common, such as New York City, Miami, and Detroit. The prevalence of HIV infection was three to four times higher in female prostitutes who were also drug users, and it was twice as high in black and Hispanic prostitutes as in white and other prostitutes.
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was 13 times higher among men than among women. However, the cited HIV prevalence rates varied widely; the maTeto-femaTe ratio of prevalence was 5.5:1 among military applicants (adjusted by age and race)
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From page 42... ...
Similarly, more than one tenth of adult cases and two tenths of pediatric cases have been diagnosed among Hispanics, who account for 6.5 percent of the national population. Estimates of HIV prevalence rates have been more variable, but the disproportion is consistent (see CDC il98Sa:Table 10~.
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Florida District of Columbia New York California ~ , for the population were 1.43 per 1,000 0.69 per 1,000 0.37 per 1,000 0.35 per 1,000 0.28 per 1,000 The five locales with the highest HIV prevalence rates among military recruits (Figure 1-2) were distribution may be different for adults and children; thus, a crude comparison of rates in two populations could be misleading if there were differences in the relative numbers of infected children.
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4) were not ranked in the top five in cumulative AIDS incidence.
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For example, Mississippi, which has one of the lowest HIV prevalence rates among military recruits (0.4 per 1,000) would be near the top of a ranking of HIV prevalence on the basis of tests of blood donors.
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From page 46... ...
In addition to the problems introduced by bias in the composition of the groups studied, the committee notes that other uncertainties about the data arise in the laboratory. The procedures used to cletermine HIV seroprevaTence in the various studies cited in the CDC i8Attempts to develop seroprevalence maps for local areas and to model HIV prevalence for regions by combining estimates from a multiplicity of screening programs and convenience samples might also be pursued.
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An ideal survey of HIV prevalence would include four steps: (1) select a probability sample from the group of interest; (2)
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be drawn, and such refusals (nonresponse) can seriously distort prevalence estimates.
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other agencies with HIV/AIDS data gathering and reporting functions review their data disclosure practices, searching for rules and setting policies that continue to safeguard confidentiality but do so at the least practical cost in information. It should be recognized, however, that no matter how strong the assurance of confidentiality and the measures to ensure it, some people will continue to refuse to furnish blood specimens (or other information)
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This contingency can be dealt with in two steps: (1) by systematically monitoring HIV testing labs to obtain information about the magnitude of the HIV false-positive rate at each facility and (2)
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As was true of all of the studies reported in CDC's 1987 review of HIV prevalence, five of the six components of the family of surveys program gather data from non-populationbased samples that cannot be generalized to any larger population of interest. 20From the appendix entitled "Summary of HHS Plan to Determine the Incidence, Prevalence and Risk Factors for HIV Infection in the United States"; see p.
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. Surveillance of IV Drug Users Two kinds of cross-sectional surveys23 will be conducted to monitor HIV prevalence among users of IV drugs: surveys of IV drug 23These surveys will supplement other studies by the National Institute on Drug Abuse (NIDA)
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, 1988:11~.24 The reason for conducting the in-treatment surveys in addition to entrant surveys is to "rapidly ascertain HIV seroprevalence by sampling IVDUs tIV drug users] currently enrolled in drug treatmentpopulations that are relatively large and accessible" (CDC/NTDA, 1988:13~.
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Yet the calculations that were used to produce these tables employ a statistical model appropriate for simple random sampling of incliviclual IV drug users, which is not the type of sampling that is being used in the survey design. If treatment centers were sampled (rather than selectecI)
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Each month a random subsample of 300 specimens will be selected independent of clinical service according to a specified age/sex stratification. The stratification ensures that equal numbers of men and women are selected within each age group, and it counteracts 26Enzyme-linked immunosorbent assay, a test used to detect antibodies against HIV in blood specimens (see the 1986 and 1988 IOM/NAS reports)
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Like the survey of IV drug users, the sentinel hospital surveillance system eschews the sampling of hospitals within the 30 metropolitan areas. Because only 40 hospitals will be chosen to participate, in most cities this surveillance system will be monitoring prevalence in one hospital, HMO, or consortium.
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determined that these components (with the exception of neonatal screening) shared the deficiency in sampling that characterizes the surveys of IV drug users and sentinel hospitals.
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Neonatal Screening The neonatal screening (CDC/NIH, 1988) is unique among the surveys planned for the 30 target cities included in the family of surveys 30Discussions with CDC staff indicate that this aspect of the plan probably resulted from attempts to guarantee anonymity at the clinic level in the blended surveys.
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The CDC/National Institutes of Health (NIH) neonatal survey will perform HIV tests using the dried blood specimens that are routinely collected from all (hospital-born)
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, there will be only a (lozen or so cases annually that will provide evidence about HIV prevalence in such subgroups. Moreover, comparisons of year-to-year changes in the number of cases will be less precise than the rates themselves.
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. Because CDC's proposed neonatal screening will provicle unbiased estimates of HIV prevalence for a population of great interest, the committee recommends that the newborn infant serm prevalence survey be extended to include all children born in the Uniter} States.
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The Components Mode} The components model was used to derive the most widely quoted estimate of HIV prevalence in the United States (see Table 1-2) , which was presented in the Public Health Service's 1986 "Coolfont Report" (Public Health Service, 1986~.
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34The prevalence rates used in these calculations were not published in the original report (Public Health Service, 1986) , but the report states that HIV prevalence estimates range from 20-50 percent for homosexual men and from 10-50 percent for users of IV drugs.
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Second, almost nothing is known about H(t) because there are such meager data about HIV prevalence.
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Each has its problems, but they are of quite different kinds. Both produce estimates of HIV prevalence of "about 1,000,000" meaning, within the range of 0.5-2 million infected persons.
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Among the most important of the attendant difficulties will be ensuring a sufficiently high rate of response to the survey. Because less than 1 percent of the population is thought to be infected with HIV, nonresponse could have a debilitating impact if it were to come disproportionately from population subgroups with elevated prevalence rates.
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Without better data, it is easy to anticipate encIless debates about whether the disease is spreading "rapidly" or "slowly." To the extent that opposing sides in these debates produce "evidence" from convenience samples, inconsistency in conclusions is to be expected, and there is thus no basis for an informative scientific debate. What we require for more informative debates, for better planning for future health care needs, and for improved evaluation of the effects of national AIDS-controT strategies are data derived from research designs that can provide reasonably unbiased estimates of the prevalence and incidence rates for HIV infection in well-defined populations of substantive interest.
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to stimulate local clinic staff to recognize the extent of HIV prevalence in their clinic ancT to adopt the Public Health Service's recommendation for routine HIV screening of all TB patients.
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While recognizing this important public health use of such data, the committee would observe that the stated objectives of this survey, as with other components of the family of surveys program, were to determine HIV prevalence and monitor trends in prevalence.37 These more demanding objectives require a survey design appropriate to these tasks. It is the opinion of this committee that the public health mandate to monitor the spread of HIV requires that reliable statistical data be gathered on HIV infection.
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(1987b) Human Immunodeficiency Virus Infections in the United States: Review of Current Knowledge and Plans for Expansion of HIV Surveillance Activities.
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(1988) HIV Seroprevalence Survey in Childbearing Women Utilizing Dried Blood Specimens Routinely Collected on Filter Paper for Neonatal Screening Programs (draft protocol)
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Public Health Reports 101:341-349. Secretary's Task Force on Black and Minority Health.
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