Analysis of False-Negative Human Immunodeficiency Virus Rapid Tests Performed on Oral Fluid in 3 International Clinical Research Studies

Abstract

Background.: The OraQuick Advance Rapid HIV-1/2 Test is a point-of-care test capable of detecting human immunodeficiency virus (HIV)-specific antibodies in blood and oral fluid. To understand test performance and factors contributing to false-negative results in longitudinal studies, we examined results of participants enrolled in the Botswana TDF/FTC Oral HIV Prophylaxis Trial, the Bangkok Tenofovir Study, and the Bangkok MSM Cohort Study, 3 separate clinical studies of high-risk, HIV-negative persons conducted in Botswana and Thailand.

Methods.: In a retrospective observational analysis, we compared oral fluid OraQuick (OFOQ) results among participants becoming HIV infected to results obtained retrospectively using enzyme immunoassay and nucleic acid amplification tests on stored specimens. We categorized negative OFOQ results as true-negative or false-negative relative to nucleic acid amplification test and/or enzyme immunoassay, and determined the delay in OFOQ conversion relative to the estimated time of infection. We used log-binomial regression and generalized estimating equations to examine the association between false-negative results and participant, clinical, and testing-site factors.

Results.: Two-hundred thirty-three false-negative OFOQ results occurred in 80 of 287 seroconverting individuals. Estimated OFOQ conversion delay ranged from 14.5 to 547.5 (median, 98.5) days. Delayed OFOQ conversion was associated with clinical site and test operator (P < .05), preexposure prophylaxis (P = .01), low plasma viral load (P < .02), and time to kit expiration (P < .01). Participant age, sex, and HIV subtype were not associated with false-negative results. Long OFOQ conversion delay time was associated with antiretroviral exposure and low plasma viral load.

Conclusions.: Failure of OFOQ to detect HIV-1 infection was frequent and multifactorial in origin. In longitudinal trials, negative oral fluid results should be confirmed via testing of blood samples.

Keywords: HIV; immunosorbent techniques; oral fluid; point-of-care testing.; serodiagnosis.

Figure 1.

Distribution of estimated delay times between human immunodeficiency virus type 1 infection and oral fluid OraQuick (OFOQ) test positivity. A and B, Delay times for the Botswana TDF/FTC Oral HIV Prophylaxis Trial (TDF2) and Bangkok Tenofovir Study (BTS) participants, respectively. Participants received either tenofovir disoproxil fumarate (TDF) or TDF/emtricitabine (FTC)-based preexposure prophylaxis (black columns) or placebo (gray columns). C, Delay time probability distribution for TDF2 and BTS. Estimated delay time calculated using the midpoint method. Data are only shown for participants with delay >0 days. The x-axis shows delay time (days); the y-axis shows counts of individuals with false-negative tests by estimated delay time (A and B) and probability density (C).

Figure 2.

Frequency distribution of potentially influential factors associated with false-negative (FN) oral fluid OraQuick (OFOQ) tests. Barplot showing count (y-axis) of OFOQ tests performed among 287 seroconverters, according to the number of contributing factors present (x-axis), from among 8 potentially influential factors associated with OFOQ tests. The proportional contribution of each factor to total bar height (test count) in each test category (false negative [FN], true negative [TN], true positive [TP]) is shown as colored bar segments. Factors shown include time to kit expiration, test operator with excess FN results, clinic site with excess FN results, antiretroviral (ARV) exposure, OFOQ test done before appearance of Western blot gp41 band, OFOQ test done before enzyme immunoassay (EIA) conversion, OFOQ test performed within 90 days of estimated time of infection, plasma viral load (pVL) <30 000 copies/mL. Tests with no factors are shown with gray bars. Data are shown for each OFOQ test performed, and individual study participants generally contributed >1 test. Missing data were assumed to be negative.