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Case 2: Discussion

Use of Rapid HIV Testing for Women in Labor

Unfortunately, some HIV-infected women present at the time of labor and delivery (L&D) without having undergone prior HIV testing; behaviors that contributed to their lack of prenatal care, such as substance abuse or mental illness, may also have placed them at increased risk for acquiring HIV. For those women who present at the time of labor without prior HIV testing, rapid HIV testing now provides a means to promptly identify previously undiagnosed HIV-infected women in whom antiretroviral therapy could provide substantial benefit in reducing maternal-to-child HIV transmission. Three rapid HIV tests are now FDA-approved and available for use in the United States: OraQuick Advance Rapid HIV-1/2 Antibody Test, Reveal G2 Rapid HIV-1 Antibody Test, and Uni-Gold Recombigen HIV Test[1]. Available data from clinical licensure trials have shown the OraQuick test to have a substantially lower proportion of false-positive results when compared with either the Reveal G2 Rapid test or the Uni-Gold Recombigen HIV Test[1]. In addition, validation testing of rapid HIV assays, including these three FDA-approaved assays, has shown variable performance based on the specific assay used and the background HIV prevalence in the setting of the testing, with Oraquick demonstrating the highest positive predictive value at all prevalence levels (Figure 1). In the Mother-Infant Rapid Intervention At Delivery (MIRIAD) study, which involved women in labor with undocumented HIV status, rapid HIV testing was well received, feasible, and performed with greater than 99% sensitivity and specificity[3]. Based on these results, along with strong evidence that antiretroviral interventions can reduce the risk of perinatal HIV transmission when initiated in labor, rapid HIV testing is recommended for all women in labor who have undocumented HIV status using an opt-out approach (perform testing unless the woman declines). If a woman in labor has a positive rapid HIV test, the clinician should initiate antiretroviral prophylaxis using intravenous zidovudine (Retrovir) without waiting for the confirmatory HIV antibody test result.

Antiretroviral Prophylactic Regimens with Presentation in Labor

Because most maternal-to-child HIV transmission occurs shortly before or during labor, HIV-infected women who present in labor with no prior antiretroviral therapy can still derive major benefit from receiving antiretroviral therapy. The decision regarding whether the mother should undergo cesarean delivery in this setting is discussed in detail in Case 3 in this same Perinatal Transmission section. The 2005 Public Health Service Task Force Guidelines lists four possible intrapartum and postpartum antiretroviral regimens for use when started in labor (Figure 2). Epidemiologic data have established benefit for women presenting in labor with the use of zidovudine alone, and clinical trials in sub-Saharan Africa have established benefit in similar situations for the combination regimen of zidovudine plus lamivudine (Epivir) and with nevirapine (Viramune) monotherapy[4,7,8,9,10]. In addition, zidovudine plus nevirapine is listed as a theoretically effective regimen. After the publication of these guidelines, results from a trial in Africa showed similar transmission rates when infants received single-dose nevirapine with or without 1 week of zidovudine; in both groups the mothers received single-dose nevirapine prior to birth if they presented early in labor[11]. The Public Health Service Task Force Guidelines have provided a detailed summary of these four regimens (Figure 3), but there are no comparative data. In the United States, the most commonly used regimen for women presenting in labor consists of zidovudine by intravenous (IV) infusion during labor and delivery, followed by 6 weeks of zidovudine oral suspension for the newborn (Figure 4). This regimen is the same as the second and third components of the Pediatric AIDS Clinical Trials Group (PACTG) 076 protocol[7]. Although it is difficult to compare results between clinical trials and observational studies and between those conducted in the United States and those in low resource countries where HIV-infected mothers often breastfeed, zidovudine appears to be equal to or superior to other regimens that have been studied for use in this setting.

Nevirapine Monotherapy with Presentation in Labor

In resource poor areas, there has been major interest and investigation in simple, cost-effective regimens that do not require the use of intravenous zidovudine or the prolonged administration of zidovudine to the infant. Nevirapine given as a single dose to the mother at the onset of labor and as a single dose to the infant within the first 48-72 hours of life reduced maternal-to-child transmission rates by approximately 50% in the HIVNET 012 clinical trial in Uganda[8]. It is inexpensive, simple, and has a good safety profile (hepatotoxicity has not been described with use of single-dose nevirapine). There are, however, increasing concerns with this regimen because of the high rates of non-nucleoside reverse transcriptase inhibitor (NNRTI) resistance that have been documented in both mother and child after only one dose or two doses of nevirapine[12,13,14]. The development of resistance is thought to result from the long half-life of nevirapine, with significant blood levels detectable for up to 3 weeks after a single dose, resulting essentially in prolonged monotherapy with an agent that has a low genetic barrier to resistance. Development of resistance may affect subsequent response to NNRTI-based regimens given for maternal therapy[17]. The recent trial from Africa noted above clearly showed a lower rate of infant NNRTI resistance when the infants took a 1-week course of zidovudine in addition to the single dose of postpartum nevirapine[11]. This study however, did not address maternal NNRTI resistance, nor did it address the impact of adding other antiviral agents, such as zidovudine, to the single dose intrapartum nevirapine. Another recently published trial from Africa showed very low rates of maternal and infant NNRTI resistance with a prepartum regimen of zidovudine plus lamivudine (started at week 32 of gestation), an intrapartum regimen of single dose nevirapine, zidovudine, and lamivudine given at the onset of labor, and a postpartum regimen of zidovudine plus lamivudine given to the infant for 3 days after birth combined with a single dose of nevirapine given on the second day[18]. Taken together, the available data strongly suggest that nevirapine monotherapy should be used only if other intrapartum prophylactic regimens are not available.

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    Figure 1 - Positive Predictive Value of a Single Screening Test for HIV in Populations with Differing HIV Prevalence* Figure 1
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    Figure 2 - Antiretroviral Regimens for HIV-Infected Women in Labor who Have no Prior Antiretroviral TherapyFigure 2
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    Figure 3 - Comparison of Intrapartum/Postpartum Regimens for HIV-1-Infected Women in Labor Who Have Had No Prior Antiretroviral Therapy Figure 3
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    Figure 4 - Intrapartum and Postpartum Dosing of Zidovudine* Figure 4