Abstract
BackgroundBecause a recent cluster of false positive results on the OraQuick ADVANCE® Rapid HIV-1/2 Antibody Test occurred in San Francisco on test kits close to their expiration date, we decided to assess the relationship between time to expiration and rate of false positive results from tests used with oral fluid.Methodology/Principal FindingsWe analyzed results of 20,904 tests with either an initial HIV-negative result (n = 20,828) or a preliminary positive result that was then negative on confirmatory tests (n = 76). We computed specificity for kits with time to expiration from ≤1 to ≥6 months, with exact binomial confidence intervals, then used logistic regression to estimate the independent association of time to expiration with false positive results, adjusting for site and technician effects. For 1,108 kits used in the last month before expiration, specificity was 98.83% (95% exact binomial confidence interval (CI) 98.00%–99.37%); the upper bound is below the claimed specificity of 99.60%. After adjustment using regression standardization for the effects of site, test lot, and technician factors, adjusted specificity in the last month before expiration was 99.18% (95% bootstrap confidence interval 98.60–99.57%).Conclusions/SignificanceWe found that specificity of the OraQuick ADVANCE® with oral fluid declined significantly with ≤1 month remaining to expiration, leaving little margin for error from other sources.
Highlights
In June of 2004, the OraQuick ADVANCEH Rapid HIV-1/2 Antibody Test (OraSure Technologies, Inc., Bethehem, PA) was approved as a CLIA-waived rapid HIV test for use with oral mucosal transudate specimens in addition to whole blood.[1]
Because California regulations required phlebotomy certification before performing a fingerstick or blood draw (California Code of Regulations 1711034; California Business and Professions Code 11240-1246.5), most communitybased testing sites in San Francisco were prevented from performing rapid HIV tests using whole blood specimens, and the advent of an oral fluid option led to a swift, significant increase in rapid testing in public HIV test sites (Facente, presented at HIV Diagnostics: New Developments and Challenges; Orlando, FL, 2005)
In the unadjusted logistic regression, the odds of a false positive result were higher for the 1,108 test kits used #1 month before expiration, compared to 1,251 kits with $6 months until expiration (Odds Ratio (OR) 14.8, 95% CI 1.94–113.6, p = 0.009)
Summary
In June of 2004, the OraQuick ADVANCEH Rapid HIV-1/2 Antibody Test (OraSure Technologies, Inc., Bethehem, PA) was approved as a CLIA-waived rapid HIV test for use with oral mucosal transudate (oral fluid) specimens in addition to whole blood.[1]. United States regulations currently require that all reactive rapid HIV tests be considered ‘‘preliminary positive’’ and confirmed in a high-complexity laboratory via Western blot (WB) or indirect immunofluoresence assay (IFA).[2] In cases where the WB or IFA is negative or indeterminate, the results are considered ‘‘discordant’’ and follow up testing is indicated This follow up testing is needed to determine whether the original reactive result was a false positive or if the patient has HIV infection but is in early seroconversion, causing the tests used for confirmation – some with lower sensitivity – to fail to detect antibodies.[3] From 2003 through early 2006 in San Francisco, all patients with discordant results were asked to submit blood specimens after one month for follow up testing according to the above protocol. Because a recent cluster of false positive results on the OraQuick ADVANCEH Rapid HIV-1/2 Antibody Test occurred in San Francisco on test kits close to their expiration date, we decided to assess the relationship between time to expiration and rate of false positive results from tests used with oral fluid
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