Kevin Delaney, MPH
Epidemiologist, Diagnostic Applications,
Behavioral and Clinical Surveillance Branch, CDC
Issue: Rapid testing for HIV provides two distinct advantages over traditional HIV testing: the ability to provide immediate results, and the ability to take testing and a test result to people and places that were previously inaccessible. Despite the fact that all FDA approved rapid test package inserts contain language stating that: “This test is suitable for use in multi-test algorithms designed for statistical validation of rapid HIV test results. When multiple rapid HIV tests are available, this test should be used in appropriate multi-test algorithms,” rapid HIV tests are currently only being used as single screening tests which require confirmation by either Western Blot or IFA.
Description: In this study, persons seeking HIV testing at a high prevalence STD clinic in Los Angeles, CA were simultaneously tested with several HIV rapid tests. Additionally both serum and plasma specimens were collected and tested with a traditional EIA and Western blot. Results of individual rapid tests and combinations of rapid tests used in sequence were compared to the results of the EIA and Western blot testing.
Lessons Learned: Nearly all individual rapid test results (13102/13129=99.8%) agreed with the results of the serum EIA and Western blot. Sensitivity of all rapid tests was greater than 98%, with nearly all falsely negative specimens coming from clients known to be HIV positive and on treatment. Adding a second, different rapid test resulted in 100% specificity for specimens that were reactive on both rapid tests, with between 0 and 4 specimens being discordant and requiring a third “tie-breaker” rapid test. The average cost of a second rapid test was approximately half the cost of a Western blot, suggesting significant cost savings are possible. A limitation of this study is the lack of follow-up information on persons with one or more positive rapid tests whose confirmatory test was negative or indeterminate.
Recommendations: Rapid test only algorithms for the diagnosis of HIV infection can be as sensitive and specific as the current diagnostic algorithm. A rapid test algorithm has the additional advantage of providing same day, point of care diagnosis of HIV infection. Given the current trend towards using a rapid test to screen for HIV infection, rapid test only algorithms also could provide significant cost savings over traditional confirmatory testing (Western Blot). Further investigations which demonstrate the use of a rapid test only diagnostic algorithm at the point of care are warranted. Such investigations should include follow-up of anyone testing positive on one or more rapid tests whose confirmatory Western blot is either negative or indeterminate.

Last Update: April 8, 2005