Performance of genotypic tropism testing in clinical practice using the enhanced sensitivity version of Trofile as reference assay : results from the OSCAR Study Group

Objective: The goal of the OSCAR programme is to evaluate the performances of genotypic HIV-1 tropism testing in clinical practice using the enhanced sensitivity version of Trafile (ESTA) as reference-assay. Methods: HIV-1 coreceptor-usage was assessed using plasma samples from 406 HIV-1 infected patients by ESTA and by gp120 V3 population-sequencing followed by Geno2pheno (set at a False Positive Rate [FPR] of 10% and 5%). Results: ESTA was successful in 365 (89.9%) samples indicating R5 in 254 (69.6%), and DM/X4 in 111 (30.4% of samples (104 [28.5%] DM and 7 [1.9%] X4). Genotypic-testing successfully assessed viral tropism for all 406 samples, including the 41 with undetermined result by ESTA. Genotypic-tropism testing at a FPR of 5% and 10% was 81.1% and 78.4% concordant with ESTA, respectively. Despite a sensitivity of 48.7% and 55.9% at a FPR of 5% and 10%, respectively, a high concordance (specificity: 95.3% for FPR of 5% and 88.2% for FPR of 10%) between genotypic-tropism testing and ESTA was reached in the detection of R5-tropic viruses. Conclusion: Our results are in line with other European studies, and support the routine use of genotypic tropism testing in clinical-settings for monitoring of HIV-1 infected patients candidate to or failing CCR5-antagonists.