The cobas® HCV GT is a new tool that accurately identifies Hepatitis C virus genotypes for clinical practice

We aimed to evaluate the correct assignment of HCV genotype/subtypes 1a and 1b by cobas® HCV genotyping (GT) assay (Roche Molecular Diagnostics) compared with nonstructural protein 5B (NS5B) sequencing.

Clinical samples from 153 patients submitted for HCV genotyping were studied. After genotyping with the cobas® HCV GT, sequencing of a 387 bp fragment in the NS5B gene and phylogenetic analysis was employed to compare genotyping results. Major discrepancies were defined as differences in the assigned genotype by cobas® HCV GT and NS5B sequencing (including genotype 1 subtypes 1a and 1b misclassification).

Overall agreement between the cobas® HCV GT and NS5B sequencing was 98%; all the 1a, 1b, 2, 3 and 4 genotypes identified by cobas® HCV GT were concordant with NS5B sequencing. Three samples tested "indetermined" by cobas® HCV GT assay and were genotyped as 1a, 3a, and 4d by NS5B sequencing.

These results indicate that the cobas® HCV GT assay correctly identifies HCV genotypes, and points out the importance of additional methods based on DNA sequencing for resolving indeterminate results.