Laboratory diagnosis of viral hepatitis C: The Sultan Qaboos University Hospital experience

Abstract

Objectives: A retrospective study was carried out to assess the performance of hepatitis C diagnostic assays in our laboratory, and to determine the prevalence of hepatitis C among blood donors at the Sultan Qaboos University Hospital.

Methods: From 1991 to 2001, approximately 55,000 serum samples collected from blood donors and patients were submitted to our laboratory for testing. All sera were screened for antibodies to hepatitis C virus (HCV) by three successive generations of the enzyme-linked immunosorbent assay (ELISA). Anti-HCV positive sera were further tested by recombinant immunoblot assay (RIBA). Reverse-transcriptase polymerase chain reaction (RT-PCR) for HCV RNA was carried out on a limited number (241) of ELISA positive samples.

Results: Out of 30012 samples from blood donors that were screened for anti-HCV, 272 (0.91%) were positive. Of these, 46.5% were confirmed positive by RIBA. The proportion of patient sera that were confirmed positive varied from 95% among intravenous drug users to 81% in patients with hepatitis to 70% in those with haemoglobinopathies. HCV RNA was detected in 67%, 6%, and 0% of the RIBA positive, indeterminate and negative samples respectively.

Conclusions: Based on RIBA, the prevalence of anti-HCV among blood donors in Oman is close to 0.5%. In our experience, RIBA-positivity is predictive of HCV infection in two thirds of subjects, and HCV infection is highly unlikely in those who are RIBA-negative. The experience at SQUH with three types of HCV assays has enabled the laboratory to develop a test algorithm, starting with screening anti-HCV ELISA.

Keywords: ELISA; RIBA; hepatitis C virus; polymerase chain reaction.

Figure 1

Genome organization of HCV and antigens licensed for diagnostic use.

Figure 2

Identity and location of HCV antigens on a nitrocellulose strip of the recombinant immunoblot assay