Evaluation of Xpert HIV-Qual assay for resolution of HIV-infection in samples with negative or indeterminate Geenius HIV-1/2 results

Background: Diagnosis of HIV infection is a multistage algorithm. Following screening with 4^th generation combination immunoassay, confirmation of HIV infection is performed with an antibody assay that differentiates HIV-from HIV-infection. In the newly updated algorithm, samples that are nonreactive or indeterminate in the differentiation assay are to be tested with an HIV-nucleic acid amplification (NAAT) test for resolution. Xpert HIV-Qual is a new NAAT assay approved for the identification of HIV infection in whole and dried blood. Objectives: To assess the performance of Xpert HIV-Qual supplementary assay in resolving the clinical status of serum samples reactive by 4^th generation immunoassays and indeterminate or negative by Geenius HIV-1/2 confirmatory assay. Study design: In a retrospective study, samples from 97 individuals for whom the true HIV-status was already known (by follow-up samples) and which were negative or indeterminate by HIV-1/2 Geenius assay were tested with Xpert Qual HIV-assay. Results: Xpert Qual assay correctly classified all 97 samples from HIV-positive (n = 49) and negative (n = 48) individuals. The sensitivity and specificity of Xpert Qual when using the true HIV status as a reference were 100% (92.7-100% at 95% confidence interval [CI] and 92.6-100% at 95% CI, respectively). Conclusions: Applying Xpert Qual HIV-assay in the new HIV multi-stage diagnostic algorithm correctly classified 100% of HIV-infections including 49 from HIV-carriers who have not yet seroconverted. With this assay the total time required for acute HIV diagnosis could be significantly reduced.