Identifying hepatitis C virus: endemic areas and estimating the viral antibody prevalence based on the prevalence of ALT elevation

To evaluate the validity of predicting the prevalence of antibodies to hepatitis C virus (anti-HCV) based on the prevalence of alanine transaminase (ALT) elevation (>40 IU/l), we conducted a community-based study. In total, 56 698 individuals underwent health examinations in 2004. Another 43 738 subjects in 2005 were the validation set. It should be valid to predict the prevalence of anti-HCV in villages (>25 participants) by the prevalence of ALT elevation. The equation was anti-HCV (%) = (% of ALT elevation - 6%)/65% (n = 487 villages, R2 = 0.58). Villages with prevalence of ALT elevation >13% had a high probability of being HCV-endemic (anti-HCV >10%). The sensitivity and specificity were 73.6 and 74.6%, respectively. By the validation set, the positive and negative predictive values were 52.0% and 79.4%, respectively. Clinical and epidemiological deductions of the equation were that baseline of ALT elevation was 6% and two-thirds of anti-HCV-positive subjects had elevated ALT.