Revising expectations from rapid HIV tests in the emergency department

Abstract

Background: Expanded HIV screening efforts in the United States have increased the use of rapid HIV tests in emergency departments. The reported sensitivity and specificity of rapid HIV tests exceed 99%.

Objective: To assess whether a reactive rapid oral HIV test result correctly identifies adults with HIV infection in the emergency department.

Design: Diagnostic test performance assessment within the framework of a randomized, clinical trial.

Setting: Brigham and Women's Hospital emergency department (Boston, Massachusetts) from 7 February to 1 October 2007.

Patients: 849 adults with valid rapid oral HIV test results.

Intervention: Rapid HIV testing with the OraQuick ADVANCE Rapid HIV-1/2 Antibody Test (OraSure Technologies, Bethlehem, Pennsylvania). Patients with reactive rapid test results were offered enzyme-linked immunoassay, Western blot, and plasma HIV-1 RNA testing for confirmation.

Measurements: Specificity and positive likelihood ratio.

Results: 39 patients had reactive results (4.6% [95% CI, 3.2% to 6.0%]). On confirmation, 5 patients were HIV-infected (prevalence, 0.6% [CI, 0.1% to 1.1%]) and 26 were non-HIV-infected (8 patients declined confirmation). The estimated rapid test specificity was 96.9% (CI, 95.7% to 98.1%). Sensitivity analyses of the true HIV status of unconfirmed cases and test sensitivity resulted in a positive likelihood ratio of 8 to 32. Western blot alone as a confirmation test provided conclusive HIV status in only 50.0% (CI, 30.8% to 69.2%) of patients at first follow-up. The addition of HIV-1 RNA testing to the confirmation protocol improved this rate to 96.2% (CI, 88.8% to 100.0%).

Limitation: Test sensitivity cannot be assessed because nonreactive OraQuick test results were not confirmed.

Conclusion: Although patients with a reactive oral OraQuick HIV screening test in the emergency department had an 8- to 32-fold increased odds of HIV infection compared with the pretest odds, the specificity of the test was lower than anticipated.

Trial registration: ClinicalTrials.gov NCT00502944.

Figure 1

Study flow diagram.

Figure 2

Posterior probability of HIV infection under alternative assumptions about the true infection status of patients with unconfirmed test results. Assumptions about the frequency of false-negative results (sensitivity) do not affect the posterior probability of infection after a positive test result.