Haptoglobin is one of five parameters (alpha2-macroglobulin, haptoglobin, apolipoprotein A1, gamma glutamyl transpeptidase, and bilirubin) used to evaluate liver fibrosis stage in the Fibrotest [29] and an inverse relationship between haptoglobin and bilirubin levels have been reported in hepatitis patients although the relationship was dependent upon the type of liver disease [30]. This evidence concerns the gene HP and hepatitis A virus infection.