Streamlining HIV testing for HIV preexposure prophylaxis.

HIV-testing algorithms for preexposure prophylaxis (PrEP) should be optimized to minimize the risk of drug resistance, the time off PrEP required to evaluate false-positive screening results, and costs and to expedite the start of therapy for those confirmed to be infected. HIV rapid tests (RTs) for anti-HIV antibodies provide results in less than 1 h and can be conducted by nonlicensed staff at the point of care. In many regions, Western blot (WB) testing is required to confirm reactive RT results. WB testing, however, causes delays in diagnosis and adds expense. The iPrEx study evaluated the safety and efficacy of daily oral emtricitabine-tenofovir disoproxil fumarate among HIV-seronegative men and transgender women who have sex with men: HIV infection was assessed with two RTs plus WB confirmation, followed by HIV-1 plasma viral load testing. During the iPrEx study, there were 51,260 HIV status evaluations among 2,499 volunteers using RTs: 142 (0.28%) had concordant positive results (100% were eventually confirmed) and 19 (0.04%) had discordant results among 14 participants; 11 were eventually determined to be HIV infected. A streamlined approach using only one RT to screen and a second RT to confirm (without WB) would have had nearly the same accuracy. Discrepant RT results are best evaluated with nucleic acid testing, which would also increase sensitivity.

Prevalence of CXCR4 tropism among antiretroviral-treated HIV-1-infected patients with detectable viremia.

Although CXCR4-tropic viruses are relatively uncommon among untreated human immunodeficiency virus (HIV)-infected individuals except during advanced immunodeficiency, the prevalence of CXCR4-tropic viruses among treated patients with detectable viremia is unknown. To address this issue, viral coreceptor usage was measured with a single-cycle recombinant-virus phenotypic entry assay in treatment-naive and treated HIV-infected participants with detectable viremia sampled from 2 clinic-based cohorts. Of 182 treated participants, 75 (41%) harbored dual/mixed or X4-tropic viruses, compared with 178 (18%) of the 976 treatment-naive participants (P<.001). This difference remained significant after adjustment for CD4+ T cell count and CCR5 Delta 32 genotype. Enrichment for dual/mixed/X4-tropic viruses among treated participants was largely but incompletely explained by lower pretreatment nadir CD4 + T cell counts. CCR5 inhibitors may thus be best strategically used before salvage therapy and before significant CD4 + T cell depletion.