Measurement of carboxy terminal peptide of type I procollagen in sera of patients with viral hepatitis and liver cirrhosis

In the present investigation, a radioimmunoassay for carboxy terminal peptide of human type I procollagen (type 1 C-peptide) was developed. Its clinical implication for serodiagnosis of hepatic fibrosis in 85 patients with viral hepatitis, 45 patients with post-hepatitic liver cirrhosis and 37 patients with alcoholic liver diseases was evaluated in comparison with that of the previously established amino terminal peptide (type III N-peptide) assay. Anti-sera against type I procollagen was obtained by immunization of rabbit with purified type I procollagen from culture medium of IMR-90. The serum level of type I C-peptide in normal subjects was found to be 42 ng/ml (s.d. = 19). Type I C-peptide levels in patients with acute hepatitis were within normal range, while in chronic hepatitis, the mean type I C-peptide level increased as the grade of fibrosis advanced from grade I to III. However, there was no statistically significant difference between the mean type I C-peptide level of grade III and that of liver cirrhosis. Increments of type I C-peptide levels were also observed in alcoholic liver fibrosis (fatty liver with fibrosis and liver cirrhosis). On the other hand, type III N-peptide assay appeared to reflect not only the degree of hepatic fibrosis, but also the degree of hepatic inflammation, giving the high levels in acute viral hepatitis. Collectively, the results indicate the usefulness of type I C-peptide assay for monitoring hepatic fibrosis in viral hepatitis as well as in alcoholic liver disease.