How does the RTRI compare to the HIV-1 LAg-Avidity EIA?
Both RTRI and LAg-Avidity EIA use the same gp41 multi-subtype protein and are based on the same principle of using limiting antigen to distinguish recent from long-term infections. However, the LAg-EIA is a laboratory-based assay requiring specialized equipment, while RTRI is a rapid test in lateral flow format and can be performed at HIV testing location, in a health facility, or in a laboratory. The performance of RTRIs in distinguishing recent from long-term infection are similar to the LAg assay at normalized optical density (ODn) cutoff of 2.0 corresponding to the mean duration of recent infection (MDRI) of 6 months for the Asante RTRI), or LAg ODn cutoff of 1.5 corresponding to an MDRI of 4 months for the Maxim Swift. However, visual reading and interpretation of RTRI can be subjective and result in inter-operator variability. Both training and certification of persons conducting TRIs and continuous quality improvement and monitoring are strongly recommended during introduction and implementation of recent infection surveillance.