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

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. 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. 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. 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

Fluctuating antibody response in a cohort of hepatitis C patients

This project was designed to longitudinally study persons who had antibodies to hepatitis C virus [HCV] to characterise the serologic course of infection. The subjects were 149 multitransfused patients [141 with thalassaemia major, 3 with thalassaemia intermedia, and 5 with sickle cell anaemia] who had been regularly followed up for 3 to 7 years. Sequential serum samples obtained semi-annually between January 1994 and January 2001 were tested, prospectively, by second or third generation HCV enzyme-linked immunosorbent assay [ELISA], followed by confirmatory recombinant immunoblot assay [RIBA-2 or RIBA-3]. Of the 149 patients, 90 did not seroconvert to HCV, whereas 59 had detectable antibodies. On the basis of RIBA results in these 59 patients, 24 [41%] had persistent high antibody levels to structural and non structural HCV antigens, 11 [19%] had persistent low antibody levels, 17 [29%] showed fluctuating antibody levels, and in 5 patients [8%] there was a total or a partial disappearance of specific antibodies [seroreversion], mainly anti-core antibodies. Two patients [3%] had antibody responses that did not fit into any of these four categories. In patients with fluctuating antibody levels, there were periods ranging from 6 months to 2 years when anti-HCV antibodies could not be detected. This study shows that the antibody response to HCV in patients who receive frequent blood transfusions is very variable. Individuals who exhibit intermittent seropositivity are a challenge to diagnosis