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 (>40IU/l), we conducted a community-based study. In total, 56698 individuals underwent health examinations in 2004. Another 43738 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, R(2)=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.