testing is done. ELISA tests done by private laboratories range from $15 to $65, but the cost to state laboratories is about $5. It costs the U.S. Army only $2.50 per serum specimen in its routine screening of all recruits because of the number tested and the established infrastructure for transporting specimens to the laboratory (all of these figures are from Mauskopf). In New York, the marginal cost of testing infant heel-stick samples for HIV is only about one dollar (Birkhead, 1998). Second, the follow-up cost for a repeatedly positive ELISA test (including the cost of the Western blot test and counseling those who are positive, but not treatment costs) is $100.

Table K.1 also shows the marginal cost of prenatal testing (per 10,000 women in prenatal care) and the cost per true positive case found. The results show that in high-prevalence areas the cost per case found is extremely low—hundreds of dollars. Even in low-prevalence areas the cost exceeds $50,000 per case found only if the marginal cost per ELISA test is $5 and the prevalence is 1 per 10,000. In a more reasonable low-prevalence scenario ($3 dollars per test and a prevalence of 2 per 10,000), the cost per case found is only $15,600.

While these numbers are not precise, they clearly indicate that universal routine HIV testing integrated into prenatal care can be very cost-effective, even in low-prevalence areas.

Strategies To Reduce Perinatal HIV Transmission

Inadequate prenatal care among women at high risk for HIV, health care providers' lack of adherence to PHS guidelines, and women's rejection of HIV testing and ZDV use all limit the ability to further reduce perinatal transmission. This section provides estimates of each potential barrier to HIV transmission reduction and presents a simplified model with which to assess the implications of different intervention strategies.

If a hypothetical population of 7,000 HIV-infected pregnant women all obtained early prenatal care; if their providers were in complete compliance with PHS recommendations regarding counseling, testing, and ZDV treatment; and if women all accepted HIV tests and ZDV treatment, and all pregnancies resulted in a live birth—the committee estimates that 350 HIV-infected babies would be born (i.e., the risk of transmission under optimal care is 5%). If, however, the onset of prenatal care, provider behavior, or other factors affecting perinatal HIV transmission are not optimal, the number of HIV-infected babies increases. Table K.2 shows the effects of varying some of the factors affecting perinatal HIV transmission. Column 2 shows the committee's estimates of the current environment: an estimated 85% of HIV-positive women seek prenatal care, 75% of women are counseled regarding HIV testing, 80% of women accept the test, 90% of HIV-positive women are offered ZDV, and 90% of women accept and comply with ZDV treatment when it is offered. Given this scenario, 1,172 babies would be born to the hypothetical cohort of 7,000 HIV-infected women, a 235% in-



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