Usefulness of antibodies Avidity Index calculation for the detection of recent HIV infection

Detecting recent HIV infection is crucial to individualize a rapid initiation of treatment. Among the laboratory methods developed to discriminate recent infections, the Anti-HIV avidity index (AI) has been shown to accurately detect <6 months HIV infections. A longitudinal retrospective study was conducted on 82 serum samples with HIV-reactive results at the WB test, collected from April 2015 through February 2017 at the “P. Giaccone” University Hospital in Palermo, Italy. A restriction algorithm was developed in order to exclude from the AI testing patients eligible for “established infection”. In the samples surviving the algorithm, the anti-HIV AI was measured with a third-generation immunoassay (Vitros Anti-HIV 1+2) and AI ratio ≤75% classified the infection as recent. After applying the restriction algorithm, only 19 of the 82 samples tested survived the exclusion parameters. For the 19 samples eligible for recent infection, the AI was calculated and in all samples (19/19, 100%) the resulting OD ratio was indicative of low avidity (AI ≤75%). Avidity test results were combined with the Fiebig staging of the sera analyzed and low avidity result correctly classified as recent infections 100% (7/7) of the p31-negative sera (Fiebig stages <VI). Based on our results, the anti-HIV AI test can be a useful tool to detected recent HIV infection (up to 6 months old), when combined with the available clinical and laboratory data.

Maria Aquilina
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