AIDS, Sexual Behavior, and Intravenous Drug Use (1989) / Chapter Skim
Currently Skimming:
Monitoring the Spread of HIV Infection
Monitoring the Spread of HIV Infection
Pages 447-470
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From page 447... ...
This manuscript is included as a background paper to the committee's report because it describes the design problems that must be solved in order to use sample surveys to monitor HIV prevalence (see Chapter 1~. Where appropriate, editorial notes have been appended to describe significant events that have occurred since the paper was prepared in 1987.
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population and the pitfalls involved in reliance upon data clerivecl from mandatory (or routine) screening of convenient populations such as applicants for marriage licenses, hospital patients, and so on.
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The instability of this fraction makes its use problematic, particularly when estimates from one subpopulation are applied to another subpopulation in which the infection may have been established for a different length of time. Multiplicative Mode} A different procedure was used to derive the most widely quoted estimate of HIV prevalence in the Unitecl States (presented in the Public Health Service's [1986]
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From page 450... ...
These estimates of population size were then multiplied by estimates of the prevalence of HIV infections among these groups in order to generate the widely quoted estimate that there are 1.0 to 1.5 million infected persons in these two groups. (The prevalence rates used in these calculations were not published but the report states that HIV prevalence estimates range from 20 to 50 percent for homosexual men and from 10 to 50 percent for users of {V drugs.)
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The usual appropriate denominators (i.e., the number of persons infected via transfusions or the total number of persons infected via transfusion who will eventually develop AIDS) were not available.
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200~. Epidemiological precedence for this approach is somewhat limited, but several factors specific to the AIDS epidemic argue for the use of national sample surveys to obtain these data.
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In addition to the requirement that HIV prevalence estimates be generalizable to the population and regularly updated, it is also desirable that the estimates permit disaggregation sufficient for prevalence (and changes in prevalence over time) to be monitored in particular demographic (and other)
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With better data such assumptions can be avoidecl.2 It follows from such considerations that proposals to initiate mandatory or routine HIV-antibody testing of hospital patients, applicants for marriage licenses, and so forth will not provide reliable evidence on the prevalence of HIV infection in the population.3 These convenient populations provide pieces of information from a larger puzzle, but they provide this information in a manner that does not readily permit us to reassemble that puzzle. We know, for example, that hospital patients are a population that is both substantially older and sicker than the general population.
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Even the most ingenious adjustments, however, could not escape the essential uncertainties of using HIV prevalence rates for persons who pass through hospitals to estimate rates for persons who are not hospitalized. Age (or other)
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. Since IV drug users are at risk of HIV infection due to needle-sharing practices, prevalence rates could be biased by the joint operation of these two factors.
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Results of HIV testing of these blood samples would provide a basis for estimating HIV prevalence in the total population and selected demographic subgroups.6 Repeated annually (or at another suitable interval) , such surveys might provide a reliable way of monitoring the spread of HIV infections in the population.
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Consider, for example, estimates of HIV prevalence for females. If 90 percent of HIV infections are assumed to be found in males, then only 150,000 of the presumed 1.5 million infected persons would be female.
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. To take one simple example of the nature of such a sample design, let us suppose that the geographic distribution of HIV infections mirrored the distribution of AIDS cases (as of April 6, 1987~.
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. Thus, the cost of an annual survey of 10,000 respondents should not scare must be exercised to ensure that decisions to decrease the sampling error of the overall estimate do not compromise the ability to obtain adequately reliable estimates of HIV prevalence in important subpopulations.
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the respondent. Respondents contacted to take part in an immunological health survey may more readily appreciate the importance of blood testing than respondents in another survey who might view an adcled request for a blood sample as irrelevant to their original commitment.
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respondents to provide blood samples. Although it may seem unusual to request that survey respondents provide blood samples, precedent suggests that such surveys are possible and do produce relatively high levels of cooperation.
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Although these factors encourage the belief that blood samples can be obtained from a substantial proportion of eligible respondents, it must be recognized that HIV blood testing is an emotionally and politically charged issue. As noted above, careful pretesting (and other measures)
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An HTV prevalence survey using a household sampling frame will, therefore, underrepresent some important subgroups (e.g., current or past IV drug users) if those subgroups are disproportionately homeless or institutionalized.
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to the central site. All blood samples should be identified only by encrypted i(lentification numbers.
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If a substantial fraction of the population (particularly groups with atypical HIV prevalence rates) feels threatened by the request to provide blood samples to interviewers from a federal
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Alternative procedures should be considered that would protect the anonymity of the survey data while permitting respondents to use the blood samples drawn in the survey to obtain information about their HIV status (together with appropriate counseling)
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However, the five attributes listed above are a reasonable starting point for vetting any strategies proposed for informing respondents of their test results. Further consideration might also be given to the option of not providing test result data in order to provide more assured protection of the anonymity of the blood test results.
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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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470 ~ BACKGROUND PAPERS Sivak, S L., and Wormser, G
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