Clinical Utility of HIV-1/2 Ab Immunochromatographic Assay as an Additive Test for HIV Screen-Positive Patients

Objective. Frequent false-positive results of current HIV screening occur due to its high sensitivity. These false-positives may delay subsequent clinical decision making. In this study, we aim to determine the usefulness of additional immunochromatographic assay (ICA) in hospitals using fourth-generation HIV-1/2 Ag/Ab assays followed by western blot (WB) confirmation. Methods. Overall, 158,431 patients' sera were screened for HIV using a fourth-generation HIV-1/2 Ag/Ab assays (Elecsys HIV combiPT) from July 2011 to May 2019. All 401 ECLIA-positive sera were re-tested using an ICA kit (SD Bioline HIV1/2 3.0 ICA), followed by WB confirmation according to national policy. Results. Sixty-five ECLIA-positive samples (65/401, 16.2%) were positive for ICA, 96.9% (63/65) of which were confirmed positive using WB. ICA results were negative in 83.8% (336/401) of ECLIA-positive samples, of which 98.5% (331/336) remained negative on WB. Five specimens (1.5%) from patients with symptoms consistent with acute HIV syndrome were false negatives on ICA. These false negatives were confirmed positive using a p24 antigen assay and nucleic acid test (NAT). Conclusions. ICA for anti-HIV Ab screen-positive specimens is helpful for earlier medical decision considering frequent false-positive results on screening. Nonetheless, ICA might be negative in acute HIV syndrome, necessitating p24 Ag assay or NAT with shorter window periods.