Fourth-Generation HIV Rapid Tests: Enhanced Sensitivity and Reduced Diagnostic Window for HIV-1 Primary Infection Screening

As most HIV rapid tests (HRT) detect only HIV-1/2 antibodies, their performance during primary HIV infection is poor. Determine HIV Early detect (Abbott) (Determine) is the only HRT with an HIV-1 p24-antigen detection, but the impact of this addition in shortening the diagnostic window remains unclear. A total of 183 HIV-1 primary infection samples were tested using the HRTs Determine and ONE STEP anti-HIV (1&2) Test (InTec Products) (One-Step). The pre-seroconversion subgroup was defined as p24-antigen positivity without Western blot nor Liaison XL (fouth generation enzyme immunoassay with distinct signal for p24-antigen and HIV-1 antibody) HIV-1 antibodies. Global sensitivity (95% CI) was 95% (91-97) for Determine versus 80% (74%-85%) for One-Step (difference p = 1.38e-06). Pre-seroconversion subgroup sensitivity was lower, at 71.9 (54.6%-84.4%) for Determine and 9.7% (3.3%-24.9%) for One-Step. Among the 45 samples with an HIV-1 infection date, no HRT was reactive up to 2 weeks. Between 2 and 3 weeks, Determine sensitivity was 78% (45%-95%) versus 56% (27%-81%) for One-Step. From 3 weeks to 1 month Determine sensitivity was 90% (62%-98%) and One-Step 45% (21%-72%). The last negative sample occurred at 3 weeks for Determine versus 70-90 days for One-Step. HRT with p24-antigen detection significantly shortens the diagnostic window from approximatively 3 months to 1 month. HRTs should be used with caution in the first month after HIV infection.