Correlation between genotypic (V3 population sequencing) and phenotypic (Trofile ES) methods of characterizing co-receptor usage of HIV-1 from 200 treatment-naïve HIV patients screened for Study A4001078

► Assessment of tropism is needed to identify patients likely to respond to maraviroc. ► Concordance between tropism testing methods in screening samples was determined. ► Phenotypic and genotypic methods reported similar frequencies of R5 and non-R5 virus. ► Most samples had non-R5 HIV-1 RNA levels of <1 log10 or ⩾4 log10 copies/mL. ► V3 genotyping is subject to fewer non-reportable results than phenotypic testing.