True and false positive HIV point of care test results in a prospective multinational study of at-risk African women: implications for large-scale repeat HIV testing in HIV prevention programs.

BACKGROUND: Accurate HIV point of care testing is the cornerstone of prevention and treatment efforts globally, though false (both negative and positive) results are expected to occur.

SETTING: We assessed the spectrum of true and false positive HIV results in a large prospective study of HIV incidence in African women using three contraceptive methods tested longitudinally in Eswatini, Kenya, South Africa, and Zambia.

METHODS: HIV serologic testing was conducted quarterly using two parallel rapid HIV tests. When one or both tests were positive, additional confirmatory testing was conducted, including HIV enzyme immunoassay (EIA) and ribonucleic acid (RNA).

RESULTS: 7730 women contributed 48,234 visits: true positive results occurred at 412 visits (0.9%) and false positives at 96 visits (0.2%). Of 412 women with HIV seroconversion, 10 had discordant (i.e., one negative and one positive) rapid tests and 13 had undetectable HIV RNA levels. Of 62 women with false positive rapid HIV results, most had discordant rapid testing but six (9.7%) had dually-positive rapid results and four (6.5%) had false positive or indeterminate EIA results. The positive predictive value of dual positive rapid results was 98.3%.

CONCLUSION: Although the majority of rapid test results were accurate, false positive results were expected and occurred in this population of initially HIV seronegative individuals tested repeatedly and prospectively. When HIV infection occurred, not all cases had textbook laboratory results. Our findings highlight the importance of confirmatory testing, particularly for individuals undergoing repeat testing and in settings where the point prevalence is expected to be low.