A multicenter evaluation of the Abbott RealTime HCV genotype II assay

Viral genotype is an important determinant of the therapeutical outcome of the chronic hepatitis C and is useful in clinical practice to determine the duration of treatment1.While the viral type shows a clear association with therapeutic success, there is currently no evidence to that effect for HCV subtype, whose value is thus confined to epidemiological studies.The Abbott RealTime HCV Genotype II assay, through the use of Minor Groove Binder probes (MGB) is able to distinguish genotypes 1 to 6 (target 5’-UTR region) and subtypes 1a and 1b (NS5B region). In four different Italian centers a comparison between the Abbott RealTime HCV Genotype II assay and the Versant HCV Genotype 2.0 (LIPA) has been performed.A total of 143 non selected samples with the request of HCV genotyping have been analysed. 141/143 samples (98.6%) have provided reportable results with both tests (2 indeterminates with LIPA). Concordance at the type level was 96.5% (136/141). Considering the 136 concordant samples, the distribution was as follows: type 1 = 61 (44.9%), 2 = 36 (26.5%), 3 = 21 (15.4%), 4 = 17 (12.5% ) 5 = 1 (0.7%). Both assays assigned subtype in 56/61 (91.8%) samples of genotype 1 (3 and 2 samples only provided the type for LIPA and Abbott, respectively) and 50/56 (89.3%) had concordant subtype. It is worth to note that 4 of the 5 samples with discordant subtype Abbott 1a/LiPA 1b came from the only center that used for LIPA the 5-UTR amplicon, loosing the benefit of the core region which has been introduced in the version 2 of the test to improve the accuracy in distinguishing between 1a and 1b.There was only one discordant sample at type level (Abbott 4, LIPA 1b) which after sequencing and phylogenetic analysis was resolved as type 4. Four mixed infections were detected, 3 with the Abbott test (two 1a+4 and one 1b+3) and 1 with the LIPA test (1a+3). In all cases the comparison test showed a single genotype 1 infection. The new Abbott RealTime HCV Genotype II assay showed a high correlation with the Versant HCV Genotype 2.0 assay (LIPA).The automation platform m2000 system (Abbott), together with objective interpretation and digital archiving results may be particularly advantageous for the laboratory.