Abstract
BACKGROUND: An alternate HIV testing algorithm has been proposed which includes a fourth-generation immunoassay followed by an HIV-1/HIV-2 antibody differentiation supplemental test for reactive specimens and a nucleic acid test (NAT) for specimens with discordant results. OBJECTIVE: To evaluate the performance of five rapid tests (Alere Clearview, Bio-Rad Multispot, OraSure OraQuick, MedMira Reveal, and Trinity Biotech Unigold) as the supplemental antibody assay in the algorithm. STUDY DESIGN: A total of 3273 serum and plasma specimens that were third-generation immunoassay repeatedly reactive and Western blot (WB) negative or indeterminate were tested with rapid tests and NAT. Specimens were classified by NAT: (1) HIV-1 infected (NAT-reactive; n=184, 5.6%), (2) HIV-status unknown (NAT nonreactive; n=3078, 94.2%) or by Multispot, (3) HIV-2 positive (n=5), and (4) HIV-1 and HIV-2 positive (n=6). Excluding HIV-2 positive specimens, we calculated the proportion of reactive rapid tests among specimens with reactive and nonreactive NAT. RESULTS: The proportion of infected specimens with reactive rapid test results and negative or indeterminate WB ranged from 30.4% (56) to 47.8% (88) depending on the rapid test. From 1% to 2% of NAT-negative specimens had reactive rapid test results. CONCLUSIONS: In these diagnostically challenging specimens, all rapid tests identified infections that were missed by the Western blot, but only Multispot could differentiate HIV-1 from HIV-2. Regardless of which rapid test is used as a supplemental test in the alternative algorithm, false-positive algorithm results (i.e., reactive screening and rapid test in uninfected person) may occur, which will need to be resolved during the baseline medical evaluation.