The OraQuick Advance Rapid HIV-1/2 Test, a point-of-care test able to detect HIV-specific antibodies in blood and oral fluid, frequently failed to detect HIV-1 infection in Botswana and Thailand, suggesting that negative oral fluid results should be confirmed by testing blood samples in longitudinal trials, according to recent study results.
“In HIV prevention trials, pre-exposure prophylaxis (PrEP) and the potentially high proportion of early infections encountered during intensive sampling may result in failure to detect infection when relying on rapid oral fluid tests.” Marcel E. Curlin, MD, from the Thailand Ministry of Public Health – CDC Collaboration in Thailand, and colleagues wrote. “The impact of a false-negative (FN) result is accentuated in this setting, since test recipients might receive PrEP regimens during established infection, or engage in unprotected sex under the false assurance of a negative result when HIV is most likely to be transmitted.”
Previously, the CDC selected oral fluid OraQuick (OFOQ) test to routine monthly HIV testing in three cohort studies that assessed men who have sex with men (MSM) and heterosexual persons at risk for acquiring HIV infection in Thailand and Botswana between 2003-2006. In this retrospective, observational analysis, researchers examined results of participants enrolled in the 3 studies to understand test performance and factors contributing to false-negative (FN) results in longitudinal studies.
Curlin and colleagues compared OFOQ results among participants becoming HIV–infected with results obtained retrospectively using enzyme immunoassay (EIA) and nucleic acid amplification tests (NAAT) of stored specimens. Researchers then labelled negative OFOQ results as true negative (TN) or FN relative to EIA and/or NAAT, and verified the delay in OFOQ conversion relative to estimated time of infection. To assess the relationship between FN results and participant, clinical and testing factors, they used generalized estimating equations.
In 80 of 287 seroconverting participants, 233 FN OFOQ results occurred. The results showed that estimated OFOQ conversation delay ranged from14.5 to 547.5 days, with a median of 98.5. The investigators observed that delayed OFOQ conversion was linked with clinical site and test operator (P < .05), PrEP (P = .01), low plasma viral load (P < .02) and time to kit expiration (P < .01). They also saw that long OFOQ conversion delay time was linked to antiretroviral exposure and low plasma viral load. There were no associations between FN results and participant age, gender and HIV subtype.
“Caution must be exercised when interpreting a negative OFOQ test in settings where acute infection is likely, where PrEP use, ART–induced viral suppression of profound immunosuppression may result in low HIV–specific antibody titers,” Curlin and colleagues wrote. “In the setting of clinical trials, investigators should consider diagnostic algorithms relying on multiple tests for detection of infection.” – by Savannah Demko
Disclosure: Curlin reports no relevant financial disclosures.