摘要AIM: To evaluate the prevalence of isolated anti-HBc in patients with chronic hepatitis C virus (HCV) infection,and its relation to disease severity.METHODS: We screened all patients with chronic HCV infection referred to King Faisal Specialist Hospital and Research Center for hepatitis B surface antigen (HBsAg), antibody to hepatitis B surface antigen (antiHBs), and anti-HBc. One hundred and sixty nine patients who tested negative for both HBsAg and anti-HBs were included in this study.RESULTS: Pathologically, 59 had biopsy-proven cirrhosis and 110 had chronic active hepatitis (CAH). Of these 169 patients, 85 (50.3%) tested positive for anti-HBc.Patients with CAH had significantly higher prevalence of isolated anti-HBc than patients with cirrhosis, 71 (64.5%)and 14 (23.7%) respectively (P ＜ 0.001). Twenty-five patients were tested for HBV DNA by qualitative PCR.The test was positive in 3 of them (12%; occult HBV infection).CONCLUSION: Isolated anti-HBc alone is common in Saudi patients with chronic HCV infection, and is significantly more common in those with CAH than those with cirrhosis. Therefore, a screening strategy that only tests for HBsAg and anti-HBs in these patients will miss a large number of individuals with isolated anti-HBc, who may be potentially infectious.