From Our 2008 Archives

False Positives in Oral HIV Test Halt Use in NYC

THURSDAY, June 19 (HealthDay News) — Due to problems with false-positive results, the use of an oral rapid HIV test was recently halted by the New York City Department of Health and Mental Hygiene, which operates 10 sexually transmitted disease walk-in clinics.

In January 2004, the clinics introduced on-site, rapid HIV testing of finger-stick, whole-blood specimens using the OraQuick test. Then, in March 2005, the clinics replaced the finger-stick test with an oral fluid test, the OraQuick Advance Rapid HIV-1/2 Antibody Test.

However, beginning in late 2005, the clinics noted an unexpected increase in false-positive oral test results. This increase subsided after several months, notes a report released online June 18 in Morbidity and Mortality Weekly Report, published by the U.S. Centers for Disease Control and Prevention.

The use of oral fluid tests was suspended for three weeks in December 2005 and replaced with the finger-stick test while city health officials investigated the increase in false-positive test results. The finger-stick tests didn't produce any false-positive results.

The oral fluid test was re-introduced in late December 2005. However, any positive result from an oral fluid test had to be followed up with a finger-stick test.

In late 2007, there was another larger increase in the incidence of false-positive oral fluid tests. The cause has not been determined and the city health department has stopped the use of the oral fluid test. Only the finger-stick test is being used.

"These findings underscore the importance of confirming all reactive HIV tests, both from oral fluid and whole-blood specimens," the report authors wrote.

"In addition, the results suggest that the NYC DOHMH strategy of following up reactive 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," they added.

— Robert Preidt

SOURCE: June 18, 2008, online release, Morbidity and Mortality Weekly Report

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