Rapid HIV Testing in Emergency Departments — Beware of False Positives

September 9, 2008

In a low-prevalence ED, rapid tests often ruled out HIV, but, when reactive,

they often yielded false-positive results.

In 2006, the CDC recommended routine HIV testing for all adults and

adolescents in all healthcare settings, including emergency departments (EDs;

AIDS Clin Care Oct 6 2006). This recommendation, coupled with the availability

of rapid HIV tests, has resulted in a variety of efforts to increase HIV

screening in EDs. However, many concerns remain (JAMA 2008; 300:945), such as

the feasibility of testing in this setting, mainly because of the resources

required (AIDS Clin Care Jan 14 2008), and the specificity of rapid oral-fluid

tests (AIDS Clin Care Jul 7 2008).

In the present study, investigators evaluated the performance of the

OraQuick Advance Rapid HIV-1/2 Antibody Test in the context of a clinical trial

conducted in a busy ED in Boston. All rapid tests were performed using oral

fluid, and all reactive tests were followed by a Western blot, an EIA, and

measurement of both CD4-cell count and plasma viral load.

During an 8-month period in 2007, 2356 ED patients were invited to

participate in the HIV testing trial; 1397 (59.3%) agreed. Of the 854 who

actually underwent rapid testing, 849 had interpretable results.

Thirty-nine patients (4.6%) had reactive tests. Of the 31 who agreed to

confirmatory testing, only 5 were found to be HIV-infected, for an overall HIV

prevalence of 0.6%; the others were catalogued as not infected. In this setting,

the estimated specificity of the test was 96.9% (95% confidence interval,

95.7%–98.1%), which was significantly lower than the specificity reported by the

manufacturer (99.8%; 95% CI, 99.6%–99.9%).

Comment: This HIV testing program was considered a success, because many

patients who otherwise would not have been tested left the ED knowing that they

were not HIV-infected. However, we clearly need better ways to confirm or rule

out the presence of HIV infection in patients whose rapid tests are reactive.

The authors suggest including viral-load testing in the panel of confirmatory

tests, along with Western blot and EIA.

— del Rio, MD

Published in AIDS Clinical Care September 8, 2008

Citation(s):

Walensky RP et al. Revising expectations from rapid HIV tests in the

emergency department. Ann Intern Med 2008 Aug 5; 149:153.

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