Abstract:
Background: HIV testing on sputum using the QraQuick HIV1/2® assay has high sensitivity and
specificity, and holds promise for application in tuberculosis surveys. Its performance under
conditions that may occur during surveys in resource-poor countries is however, unknown. We
assessed, in a blinded comparison with HIV serum testing, the sensitivity and specificity of the
OraQuick® assay for detecting HIV antibody in sputum specimens kept at ambient temperature for
up to 7 days, with and without decontaminant.
Methods: Paired sputum and blood specimens from consecutively diagnosed smear-positive
tuberculosis patients were tested with OraQuick® and 2 HIV-1/2 ELISA's. Sputum was tested within
24 hours of collection, split into 2 aliquots with and without addition of cetylpyridium chloride, and
tested again after 4 and 7 days.
Results: Complete data was available for 377/435 (87%) enrolled patients; 132 (35%) tested HIV
positive on serum. The sensitivity of the sputum test was 94.7% (95% CI 89.4–97.8) on day 1, 93.2%
on day 4 and 92.9% on day 7. The specificity was 92.9% (95% CI 88.9–95.8) on day 1, and declined
to 76.7% on day 4 (p < 0.001) and to 62.7% on day 7 (p < 0.001). Adding cetylpyridium chloride
further decreased the specificity to 67.8% on day 4 (p = 0.04) and to 49.6% on day 7 (p = 0.004).
Conclusion: Transportation of sputum specimens at ambient temperatures for 4 days or more,
and addition of decontaminant, strongly affect the specificity of the OraQuick® assay. Unless applied
within one day, this assay is not suitable for estimation of HIV-prevalence among tuberculosis
patients in survey settings.
