Evaluation of a BioRad Avidity assay for identification of recent HIV-1 infections using dried serum or plasma spots.

Serological methods to differentiate between recently acquired and established HIV-1 infections are a useful tool in the HIV-surveillance to characterize the epidemic, identify groups at risk and assess HIV-preventive interventions. Therefore, an avidity-based, modified BioRad Genscreen™ HIV-1/2 assay (BRA) was evaluated according to the avidity-based, modified BioRad HIV-1/2 Plus O protocol (BRA). Overall, 692 well defined samples (82.5% B and 17.5% non-B subtypes) from recent (<180 days, n = 239), intermediate (181-364 days, n = 35) or long term infections (≥365 days, n = 419) were used to determine a 'mean duration of recent infection' (MDRI), a 'median DRI' (MdDRI), the false recent rate (FRR), and concordance between the BRAs and the Sedia BED HIV-1 Capture enzyme immunoassay (BED). The optimal avidity index cut-off was determined to be 70% resulting in an MDRI of 233 days (95% IQR: 174-351) and an MdDRI of 171 days (95% IQR: 142-212). Concordance with the BRA was high with 96.4%. The FRR of 6.0% as well as the MdDRI are similar to the BED (8.4%; 170 (139-214) days). Therefore, the BRA is a suitable alternative to replace the BED and trend analysis will be feasible after minimal adjustments for the MdDRI and the MDRI.