[Comparison of two hepatitis C virus typing assays in a Tunisian population]

In patients with hepatitis C, it is necessary to determine the genotype of the hepatitis C virus (HCV) to tailor treatment schedules. HCV-positive sera from 60 chronically infected patients were analyzed by two methods: serotyping and genotyping, to evaluate the suitability of serotyping method for routine determination of HCV genotype; 47 men and 13 women were included in this study, nine were renal transplant patients and five were hemodialysis patients. Anti-HCV antibodies were detected by Elisa (HCV Ab III, Innogenetics SA) and confirmed by immunoblot assay (INNO-LIA-HCV Ab III update, Innogenetics SA). Genotyping analysis was performed by a line probe assay (Inno-LiPA-HCV, Innogenetics SA) and serotypes were determined by an Elisa-based serotyping assay (Murex HCV serotyping 1-6 HCO2, Murex SA) which detect type specific antibodies against NS4-derived epitopes. Among 60 patients positive for anti-HCV antibodies and confirmed by immunoblot assay only 90% show a strong reactivity with NS4. We found the following genotype distribution : 1b (73.3%), 4 (10%), 1a (5%), 3a (5%), 4c/4d (5%) and 1 not classified (1.7%). The most prevalent serotype was type 1 (60%) followed by serotype 6 (20%), 4 (8.3%), 2 (1.7%) and 10% were no type specific antibodies. The sensitivity of the serotyping and the genotyping assays was 90% with a total concordance of 68.3%. Thirteen samples revealed discrepant results with genotype : 1b (4), 1a (3), 3a (3), 4 (2) and 4c/4d (1). This study indicates that the serotyping assay is less specific than genotyping. However, the test is rapid, relatively easy to perform and represent a reliable alternative in laboratories that lack the specific expertise to typing the HCV by molecular methods.