This memo is an update to the July 2016 memo to provide recent information for Arizona clinicians and HIV testers who use the Alere [Abbott] DetermineTM HIV-1/2 Ag/Ab Combo Rapid Test. This update is based on recent studies and the October 2017 technical update from the Centers for Disease Control and Prevention (CDC).
The Determine Combo is designed to separately detect HIV-1 p24 antigen and HIV-1/2 antibodies in plasma, serum or whole blood specimens, including fingerstick. When used with serum or plasma, it is a moderate complexity test under CLIA (the Clinical Laboratory Improvement Amendments), restricting its use to laboratories. Studies show that, although the single-use Determine Combo rapid test with plasma is less sensitive during early HIV infection than instrumented Ag/Ab combo tests, it detects HIV infection earlier than many other FDA-approved antibody-only HIV tests. In situations where instrumented antigen/antibody tests are available, these tests are preferred over Determine Combo due to their superior sensitivity for detecting HIV during acute infection. However, for laboratories that wish to use Determine Combo as the screening test in the laboratory algorithm for HIV diagnosis, performing the Determine Combo rapid test on serum or plasma may be a useful option, particularly for smaller labs that perform a low volume of HIV tests, because it offers short turnaround time, high antibody sensitivity, and moderate sensitivity for p24 antigen.
With whole blood specimens, the Determine Combo is CLIA-waived, making it suitable as a point-of-care (POC) rapid HIV test in clinics and outreach testing sites. However, studies indicate that, while Determine Combo used on whole blood detects HIV antibodies earlier than many other FDA-approved rapid antibody tests, its sensitivity for p24 antigen is suboptimal: it does not reliably detect acute infection. The attached fact sheet provides more details on the results of studies in different contexts. For more information or to request HIV training, please contact Alyssa Guido at firstname.lastname@example.org or (520) 626-0723.