Rapid Oral HIV Test Less Sensitive vs Rapid Blood When HIV Rate Low

Oraquick, the rapid HIV test, had slightly lower sensitivity and positive predictive value in low HIV prevalence regions than in high-prevalence regions when used on oral specimens than when used on blood samples, according to results of a systematic review and meta-analysis.

Rapid HIV testing has become a cornerstone of HIV screening throughout the world. Researchers planned this study to determine whether the Oraquick Advance Rapid HIV-1/2 test works as consistently in oral samples as in blood samples.

The investigators searched five databases of published work and reviewed databases of five key HIV meetings. All studies analyzed focused on adults at risk of HIV. The analysis excluded studies in children and coinfected populations, studies with self-reported inferior reference standards, and studies with incomplete reporting of key data.

Pooled sensitivity of the rapid HIV test was almost 2% lower in oral fluid (98.03%, 95% confidence interval [CI] 95.85 to 99.08) than in blood samples (99.68%, 95% CI 97.31 to 99.96). Specificity of the rapid test was similar in oral specimens (99.74%, 95% CI 99.47 to 99.88) and in blood (99.91%, 95% CI 99.84 to 99.95). (Sensitivity is the ability of the test to single out people with HIV. Specificity is the ability of the test to classify people who do not have HIV as negative.)

Negative likelihood ratios were small and similar in oral specimens (0.019, 95% CI 0.009 to 0.040) and blood (0.003, 95% CI 0.001 to 0.034). But positive likelihood ratios were lower in oral specimens (383.37, 95% CI 183.8 to 799.31) than in blood (1105.16, 95% CI 633.14 to 2004.37).

Positive predictive values were similar with oral and blood specimens in settings with high HIV prevalence (oral 98.65%, 95% CI 85.71 to 99.94; blood 98.50%, 95% CI 93.10 to 99.79). But in low-prevalence settings, positive predictive values were lower in oral samples (88.55%, 95% CI 77.31 to 95.87) than in blood (97.65%, 95% CI 95.48 to 99.09).

The authors caution that “the slightly lower sensitivity and positive predictive value in low-prevalence settings in oral specimens should be carefully reviewed when planning worldwide expanded initiatives with this popular test.”

They note that “the lower sensitivity of the test in oral mucosal transudate compared with blood specimens is probably because of a lower quantity of HIV antibodies in oral mucosal transudate than in whole blood. The titre of HIV antibodies is also low in acute HIV infection before seroconversion, hence the increased possibility that oral testing might miss more acute HIV infections than tests with blood specimens because of its lower sensitivity.”

Source: Nitika Pant Pai, Bhairavi Balram, Sushmita Shivkumar, Jorge Luis Martinez-Cajas, Christiane Claessens, Gilles Lambert, Rosanna W Peeling, Lawrence Joseph. Head-to-head comparison of accuracy of a rapid point-of-care HIV test with oral versus whole-blood specimens: a systematic review and meta-analysis. Lancet Infectious Diseases. 2012; 12: 373-380.

For the study abstract

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Written by Mark Mascolini on behalf of the International AIDS Society