Evaluation of a Sensitive/Less Sensitive Testing Algorithm Using the bioMérieux Vironostika-LS Assay for Detecting Recent HIV-1 Subtype B' or E Infection in Thailand

The performance of the bioMérieux Vironostika-LS EIA (less sensitive enzyme immunoassay) was assessed to detect recent seroconversion among injecting drug users (IDUs) in Bangkok, Thailand who were infected with either HIV-1 subtypes B' or E (also known as circulating recombinant form CRF01_AE). To evaluate the Vironostika-LS EIA in non-B subtypes, we collected longitudinal specimens (n = 796) from 115 IDUs (subtype B' infection, n = 24; subtype E infection, n = 91). After testing HIV-positive specimens with the Vironostika-LS EIA, standardized optical densities (SODs) were calculated using median values to determine the window period, which is the time from seroconversion on a standard EIA to seroconversion on the Vironostika-LS EIA for a given SOD, for either subtype. For an SOD cutoff of 1.0, Vironostika-LS EIA results showed a mean window period of 239 days (95% confidence interval [95% CI], 208–287 days) for subtype B' and 356 days (95% CI, 318–402 days) for subtype E in Thailand. This outcome demonstrates that the Vironostika-LS EIA has significantly different performance characteristics in detecting recent seroconversion between different HIV-1 subtypes. Accurate identification of recent infection and estimation of incidence for HIV-1 strains other than North American subtype B, using the Vironostika-LS EIA, requires knowledge of specimen subtype and use of appropriate cutoffs and mean window periods.