Background Currently, 24 out of 39 laboratories in Quebec use the AxSYM HIV Ag/Ab Combo for HIV screening. This kit will be discontinued December 2013 and three novel 4th generation screening HIV assays (Architect, Roche Elecsys HIV Combi and ADVIA CENTAUR), approved by Health Canada, represent the alternative to AxSYM.

Objective and Methods: To investigate the performance of these 3 novel screening HIV Combo assays, in 6 clinical sites from Quebec. A total of 150 samples from patients with documented acute infection, a panel of 25 Seracare HIV-1 specimens, 3 quality control specimens (HIV-1.2 Ab POS, p24Ag POS, HIV-1.2 NEG), and 5577 sera from routine diagnostic patients were tested.

Results Sensitivity assessment- The 3 novel combos demonstrated comparable 100% sensitivity. Confirmed positive samples on the Architect and Roche Elecsys presented much greater S/CO values than AxSYM.

Specificity assessment- Each novel combo was compared separately to the AxSYM. Discordant results were confirmed using supplemental confirmatory assays.

The specificity of Architect was evaluated using 1099 specimens: 1095/1099 were non reactive, 3/1099 were reactive and 1/1099 was discordant. For Roche Combo, 3282 specimens were tested: 3222/3282 were non reactive, 41/3282 were reactive, and 19/3282 were discordant. The Advia Centaur was evaluated using 1196 specimens, 1177/1196 were non reactive, 12/1196 were reactive and 7 were discordant.

Amongst the 66 specimens that were reactive with novel and AxSYM combos, 52 (79%) were confirmed positive. All discordant results were confirmed negative. The 5494 specimens that were negative with both kits (novel and AxSYM) demonstrated lower S/CO values on Architect and Roche than on AxSym.

Conclusions The 3 novel HIV Ag/Ab Combo demonstrated good performance (sensitivity, specificity and concordance) with better segregation of positive and negative samples than AxSYM. All 3 kits represent a good alternative to the AxSYM.