HIV incidence estimates for three clinical cohorts in the United States.

The table shows cross-sectional and longitudinal incidence estimates for three clinical cohorts (see Methods); 95% confidence intervals are shown in parentheses. Longitudinal incidence estimates were calculated as the number of seroconversion events divided by the number of person-years of follow-up; these estimates were reported previously [26], [29]–[30]. The % difference is defined as: 100× (the absolute value of the difference between the longitudinal incidence estimate and the cross-sectional incidence estimate) divided by the longitudinal incidence estimate. Cross-sectional incidence estimates were obtained using five testing approaches (the original LAg-Avidity protocol, the revised LA-Avidity protocol, the 3-assay MAA in Table 2, and MAA #1 and MAA #2, described in Figure 2). The following units were used for the component assays: LAg-Avidity assay: normalized optical density units (OD-n); BioRad-Avidity assay: percentage (avidity index); viral load: copies/mL; CD4 cell count: cells/mm3.a In HPTN 061, some study participants who contributed to the longitudinal incidence estimate did not complete the 12-month study visit or did not have a sample stored at that visit and were not included in the cross-sectional incidence estimates.b In HPTN 064, the primary study outcome was overall HIV incidence, measured as a composite incidence estimate that took into account cross-sectional incidence at enrollment (estimated using a MAA), acute infections at enrollment, and observed incidence during longitudinal follow-up (based on HIV seroconversion). The overall HIV incidence in the HPTN 064 study was 0.32% (95% CI: 0.14–0.74%) [30]. In that study, cross-sectional incidence was assessed using a MAA that included the BED-CEIA, the BioRad-Avidity assay, CD4 cell count, and HIV viral load [43].c For HPTN 064: A total of 38 women were identified with HIV-infection in the HPTN 064 study. The 33 HIV-positive women included in the cross-sectional incidence assessment at 6–12 months included 28 women who were seropositive at study enrollment, one woman who had acute HIV infection at enrollment, and four women who acquired HIV infection during the study. For HIVNET 001: All participants included in the cross-sectional incidence assessment were HIV-uninfected at study enrollment. For HPTN 061: The 246 men included in the cross-sectional incidence assessment at 12 months included 218 men who were seropositive at study enrollment, three men who had acute HIV infection at enrollment, and 25 men who acquired HIV infection during the study.d Incidence estimates using these testing approaches were calculated using window periods recommended by the manufacturer of the LAg-assay.e Incidence estimates using the two optimized MAAs (MAA #1 and MAA #2) were calculated using window periods determined in this report (Table 3).