Comparative quantification of diverse serotypes of HIV-1 in plasma from a diverse population of patients

HIV-1 is characterised by extensive genetic variability encompassing at lea st 10 different phylogenetically related clades within the major group of H IV-1 subtypes. Most commercially available HIV-1 RNA plasma viral load assa ys have been optimised with clade B viruses and may yield misleadingly low RNA levels for non-clade B viruses that are increasingly found in Europe. I n this study we compare the most recent versions of the Roche Amplicor HIV Monitor and the Chiron Quantiplex for ability to detect viraemia in a popul ation of patients infected with a range of HIV-1 subtypes. EDTA-treated pla sma was obtained from 206 patients. The Amplicor and Quantiplex assays were carried out in accordance with manufacturers' instructions. Results from 5 3/206 (25.7%) samples differed by >0.4 log between Amplicor 1.5 and Quantip lex 3.0. A >0.5 log and 1.0 log difference was detected between Amplicor 1. 5 and Quantiplex 3.0 in 37/206 (17.9%) and 7/206 (3.4%) of samples, respect ively. Overall, Amplicor 1.5 gave a median value of 0.22 log higher than Qu antiplex 3.0. Discordant results were detected in 53 out of 206 (25.7%) sam ples. Of these 22 out of 123 (17.9%) samples were of UK origin, 18 out of 4 3 (41.9%) African, 1 out of 8 (12.5%) South American, 1 out of 6 (16.7%) No rth American, 4 out of 9 (44.4%) North European, 3 out of 11 (23.7%) South European and 3 out of 7 (42.3%) Asian samples, respectively. Serotyping rev ealed that discordant viral load results between Amplicor 1.5 and Quantiple x 3.0 occurred within sam plea from all subtypes (A-E). Despite the improve ments made to both the Roche Amplicor and the Chiron Quantiplex assays disc ordant results were detected between the two assays in 25.7% of cases. In a substantial minority of patients there were major discrepancies between th e two assays that were not explained by HIV subtype differences. J. Med. Vi rol. 62:445-449, 2000. (C) 2000 Wiley-Liss, Inc.