Reliable resolution of ambiguous genotyping results of hepatitis C virus genotype 1 with the Abbott HCV Genotype Plus RUO assay. HCV genotype 1 subtyping with commercial and reference assays

Accurate subtyping of hepatitis C virus genotype 1 (HCV-1) remains clinically relevant. The Abbott HCV Genotype Plus RUO (GT Plus) assay, targeting the core region, was evaluated as a reflex test to resolve ambiguous HCV-1 results. 198 HCV-1 specimens were analyzed with GT Plus (38 specimens with and 160 without subtype assigned by the Abbott RealTime Genotype II (GT II) assay targeting the 5'NC and NS5B regions). Sanger sequencing and phylogeny of the core and/or NS5B regions were performed in 127 specimens without subtype assignment by GT II, “not detected” results by GT Plus, or with mixed genotype/subtype infections. The remaining GT Plus results were compared to LiPA 2.0 (n=45) or to previous GT II results (n=26). Potential mixed 1a plus 1b infections (n=7) were not confirmed by next-generation sequencing. The GT Plus successfully assigned the subtype in 142/160 (88.8%) samples. “Not detected” results indicated other HCV-1 subtypes or genotypes or were due to mismatches in the core region in subtype 1b. The subtyping concordance between GT Plus and either sequencing or LiPA was 98.6% (140/142). Therefore, reflex use of the GT Plus assay represents a reliable and simple approach to considerably reduce ambiguous HCV-1 results.