Muhammad Idrees.
Comparison of Two Typing Systems for Genotyping of Hepatitis C Virus Isolates.
J Coll Physicians Surg Pak Jan ;11(11):679-83.

Objective: To determine the suitability of a commercial serotyping assay (Murex HCV serotyping 1-6 assay, Murex, Burgwedel, Germany) and genotype-specific PCR assay for the routine determination of HCV genotypes. Design : A comparative study. Place and Duration of Study: The present study was carried out at Division of Molecular Diagnostics, The Medical Laboratory, Lahore, Pakistan from September 1999 to June 2000. Subject and Methods: During the course of this study, HCV-RNA positive sera samples from 50 chronically infected patients were characterized by serotyping and genotyping assays. Genotyping assay utilized type-specific primers for amplification of the core region, whereas serotyping assay detected type-specific antibodies of the NS4 portion of HCV. Results: Out of the total tested serum samples, serotype-specific antibodies were detected in 36 (72%) whereas type-specific PCR fragments were observed in 48 (96%) serum samples. There was 68% correlation between the two typing assays. Only 16 (32%) samples revealed discrepant results as follows: i) twelve untypable samples by serotyping assay showed type-specific PCR bands by genotyping assay, ii) in two samples with double infections showed by serotyping, only one genotype was detected, iii) in one sample the serotype was completely different from the genotype; iv) in one sample with two genotypes, only one serotype was detected. One PCR and anti-HCV positive sample was untypable by both the typing systems. Conclusion: Both the systems are accurate, reliable and feasible for HCV typing on routine basis. Serotyping assay has the advantages of rapid test procedure and requirement of few instruments. However, the serotyping assay has low specificity and sensitivity, especially for serotype 3 (P<0.001), which is predominant in Pakistan and lacks the possibility of HCV subtyping. HCV subtyping can only be achieved by genotyping assays. In addition serotyping assay cannot differentiate between current and resolved HCV infection.

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