Introduction: Sero-epidemiological studies of herpes simplex virus type-2 (HSV-2) infection in Africa remain difficult to interpret owing to the high rate of false-positive results observed when using the new recombinant gG2 HSV-2 ELISA tests. We compared the performance of two widely used gG2 ELISAs to derive an appropriate testing algorithm for use in South Africa.
Methods: Sera from 210 women attending family planning clinics in Johannesburg were tested using HerpeSelect® and KalonTM HSV-2 gG2 assays. Sera from 19 discordant pairs, 44 concordant positive and 33 concordant negative samples were further tested by HSV Western Blot (WB). Sensitivity and specificity of each test and of combination algorithms compared to WB were calculated.
Results: HerpeSelect® had a sensitivity of 98% (95% confidence interval [CI]: 95-100) and specificity of 61% (95%CI: 48-74). Kalon™ was less sensitive (89%, 95%CI: 83-94) but more specific (85%, 95%CI: 61-100). Seroprevalence may have been overestimated by as much as 14% by HerpeSelect®. Specificity was improved by raising the cut-off index for determination of a positive result for HerpeSelect® (to ≥3.5), but not for Kalon™. HIV-1 infection reduced the specificity of HerpeSelect® to 30%. Improved sensitivity and specificity were obtained by a two-test algorithm using HerpeSelect® (≥3.5) as the first test and Kalon™ to resolve equivocal results (sensitivity 92%, 95%CI: 82-98; specificity 91%, 95%CI: 79-98).
Conclusion: Newer HSV-2 serological tests have low specificity in this South African population with high HIV-1 prevalence. Two-step testing strategies could provide rational testing alternatives to WB.