Variation in serum type III procollagen peptide with age in healthy subjects and its comparative value in the assessment of disease activity in children and adults with chronic active hepatitis.

To determine the comparative value of serum Type III procollagen peptide (PIIIP) in paediatric and adult liver disease we have measured PIIIP in 201 healthy subjects (aged 1 day-77 years) and twenty-one children and five adults with chronic active hepatitis (CAH). Healthy children had significantly higher PIIIP levels than adults (P less than 0.001), with highest values of 298 +/- 88 ng ml-1 (s.d.) in the neonatal period. PIIIP fell to 30.9 +/- 7.0 by 1 year, 19.1 +/- 4.5 by 3 years and rose significantly (P less than 0.01) at puberty. Adult levels (8.3 +/- 3.2) occurred by 16 years of age. Serum PIIIP levels were significantly elevated (P less than 0.001) in adults when they had biochemical and histological evidence of active liver disease but were consistently within the normal range for age in 70% of children with similar hepatic pathology. The minor elevations in PIIIP in the other children were unrelated to clinical, biochemical or histological evidence of active liver disease. While raised PIIIP may be a non-invasive marker of liver disease activity in adults, its value in childrens' disorders appears to be limited by the high levels of PIIIP which occur during growth.