Introduction Sero-epidemiological studies of herpes simplex virus (HSV) type 2 infection in Africa remain difficult to interpret as a result of the high rate of false-positive results observed when using the new recombinant gG2 HSV-2 ELISA tests. The performance of two widely used gG2 ELISA was compared 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 Kalon HSV-2 gG2 assays. Sera from 20 discordant pairs, 44 concordant positive and 33 concordant negative samples were further tested by HSV Western blot. The sensitivity and specificity of each test and of combination algorithms compared with Western blot were calculated.
Results HerpeSelect had a sensitivity of 98% (95% CI 95 to 100) and specificity of 61% (95% CI 48 to 74). Kalon was less sensitive (89%, 95% CI 83 to 94) but more specific (85%, 95% CI 61 to 100). Seroprevalence may have been overestimated by as much as 14% by HerpeSelect. Specificity was improved by raising the cut-off index for the 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 to 98; specificity 91%, 95% CI 79 to 98).
Conclusion Newer HSV-2 serological tests have low specificity in this South African population with a high HIV-1 prevalence. Two-step testing strategies could provide rational testing alternatives to Western blot.
- Herpes simplex virus type 2
- HSV serology
- South Africa
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Partial presentation of this work: 16th Biennial Conference of the International Society for Sexually Transmitted Diseases Research, Amsterdam, 2005.
Funding The study was supported by grants from the UK's Department for International Development (DFID) office in Pretoria, South Africa, and the UK's DFID-funded Knowledge Programme on HIV/AIDS and STI of the London School of Hygiene and Tropical Medicine. Western blot testing was supported by NIH grant AI30731.
Competing interests RAM has received research grants or contracts, honoraria or consulting fees during the last 3 years from Biokit, Bio-Rad Laboratories, Biovail, Focus Diagnostics and GlaxoSmithKline. The remaining authors report no competing interests.
Ethics approval This study was conducted with the approval of the University of the Witwatersrand Human Research Ethics Committee, South Africa and the London School of Hygiene and Tropical Medicine Ethics Committee, UK.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.