Diagnosis of HIV-1 infection: Performance of Xpert Qual and Geenius supplemental assays in fourth generation ELISA-reactive samples

Background: Architect (AR) and Vidas (VD) fourth generation HIV screening immunoassays, which identify early stages of HIV infections, could have false positive results especially at low signal/cutoff (S/C) AR values. Geenius HIV1/2 (GS) is a specific confirmation line immunoassay that is not highly sensitive to early HIV infections. An HIV-1 RNA assay may better detect such infections.

Objectives: To evaluate all AR-VD reactive samples with GS results, and to assess Xpert Qual HIV-1 RNA assay (XQ) as an alternative to GS, in the first low S/C AR-VD-reactive samples from a tested individual.

Study design: First AR-VD-reactive-GS-tested results from all individuals with resolved HIV status, collected between March 2015 and March 2017 (n = 749), were retrospectively assessed. Samples with AR-VD-reactive-GS-discordant results and those with low S/C AR-VD-reactive results, were tested by XQ. Receiver operating characteristic (ROC) analysis of GS and XQ sensitivity/specificity was performed.

Results: Overall, 94.1% (705/749) of AR-VD-reactive results were true HIV-1 positive. All samples with <3 S/C AR values were false positive. XQ resolved all first samples with AR-VD-reactive-GS-discordant results. The diagnostic accuracy of XQ in low (≤33 S/C) AR-VD-reactive samples was better than that of GS (97.6%, 81/83 versus 73.5%, 61/83, p < 0.01). ROC analysis for low S/C AR samples was optimal for pooled XQ and GS results.

Conclusions: Incorporating XQ in the current screening algorithm for the first AR-VD-reactive-GS-discordant samples may significantly reduce overall turn-around time of HIV-1 diagnosis.