Background Specimens collected in Pretoria for the FEM-PrEP study, a phase III trial on pre-exposure prophylaxis for HIV prevention among African women, were tested for Herpes Simplex Virus type II (HSV-2). We present here the performance of the Focus HerpeSelect and Kalon HSV-2 gG2 ELISA.

Methods The HSV-2 infection was determined in 701 women at baseline with two IgG ELISAs: Kalon HSV-2 gG2 ELISA (Kalon Biologicals Ltd.) and HerpeSelect HSV IgG ELISA (Focus Technologies). Participants were considered true positive for HSV-2 when specimens were reactive in both assays. In order to determine incident HSV-2 infections during the study, specimens collected at final visit (i.e. after 52 weeks/at product interruption visit) of participants being HSV-2 seronegative at baseline were tested using the same assays.

Results At baseline, 287 and 315 positive results were found using the Kalon- and Focus assay, respectively. All Kalon positives were also positive in the Focus assay and considered to be true infections (initial prevalence: 40.9%). Of the 28 specimens positive with the Focus only, 10 of them became true positive at final visit. We therefore assume that the Kalon missed 10 infections and, the Focus detected falsely 18 positives at baseline, resulting in a final HSV-2 prevalence of 42.4% at baseline. At final visit, an additional 33 new infections were found. At baseline we obtained a sensitivity of 100% (95% CI: 98.8–100) and 96.6% (95% CI: 93.9–98.4) and a specificity of 95.5% (95% CI: 93.1–97.3) and 100% (95% CI: 99.1–100) for Focus and Kalon respectively.

Conclusion Although our study confirms the assay performance findings of previous studies in Sub-Saharan countries, we found less pronounced differences in terms of sensitivity and specificity of both assays using the cut-off as prescribed by the manufacturers. The prevalence of HSV-2 found in our study corresponds to previously reported results.