Beware the False-Positive Oral Fluid Rapid HIV Tests
In January 2004, New York City Department of Health and Mental Hygiene (NYC DOHMH) STD clinics introduced anonymous, on-site rapid HIV testing of finger-stick whole-blood specimens using the OraQuick® brand test, one of six rapid HIV tests approved by the Food and Drug Administration (FDA) since 2002. In March 2005, the clinics replaced finger-stick whole-blood testing with oral fluid testing with the OraQuick Advance Rapid HIV-1/2 Antibody Test. The clinics use Western blot confirmatory tests on serum to confirm all preliminarily positive whole-blood or oral fluid rapid tests.
In late 2005, an unexpected increase in the number of false-positive oral fluid tests occurred, but the increase subsided after several months. In December 2005, while the cluster of false-positive oral fluid test results was being investigated, the NYC DOHMH Bureau of STD Control temporarily suspended oral fluid testing in the clinics for 3 weeks and replaced it with finger-stick whole-blood rapid testing, which produced no false-positive test results. On December 21, 2005, NYC DOHMH resumed oral fluid rapid testing but also introduced immediate follow-up with the more reliable finger-stick whole-blood testing after any preliminarily positive oral fluid test result.
In November 2007, a larger increase in the incidence of false-positive oral fluid rapid test results occurred and stretched through April 2008, prompting the NYC DOHMH to suspend the use of oral fluid testing in STD clinics. During this period, nearly half of reactive oral fluid tests in the STD clinics were false-positives, which is well beyond the manufacturer’s expectations for the product. Currently, despite the popularity of non-invasive oral HIV on-site rapid testing with clinic patients and the convenience for staff members, finger-stick whole-blood testing is now the only rapid HIV test being offered in these New York City clinics.
The cause for the episodic increases in false-positive oral fluid tests remains undetermined. The Center for Disease Control continues to encourage the use of rapid HIV tests, because they increase the number of individuals who are tested and who receive their results. The NYC DOHMH findings emphasize the importance of confirming all preliminarily positive HIV tests, both from oral fluid and whole-blood specimens. In addition, the results suggest that the NYC DOHMH strategy of following up preliminarily positive oral fluid test results with an immediate finger-stick whole-blood test reduced the number of apparent false-positive oral fluid test results and might be a useful strategy in other settings and locations.
--Summarized by Barrett Robinson, MD, MPH
Barrett Robinson is a Maternal-Fetal Medicine Fellow at Northwestern Memorial Hospital, where he participates in the ongoing care of one of Illinois’ largest clinics exclusively servicing HIV-positive pregnant patients
Citation:
“False-Positive Oral Fluid Rapid HIV Tests—New York City, 2005—2008.” MMWR Weekly. June 20, 2008/ 57 (24);660-665.
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Abstract
