Serum concentration of procollagen type I carboxyterminal propeptide in systemic sclerosis.

The serum level of procollagen type I carboxyterminal propeptide (P1CP), which has been used as an index of collagen synthesis in patients with various fibrotic diseases during the active stage, was measured using enzyme-linked immunosorbent assay in 61 patients with systemic sclerosis (SSc) and in 21 control subjects. The mean P1CP level in the SSc patients was significantly higher than in the normal controls (mean +/- SD, 326 +/- 319 vs 128 +/- 87 ng/ml; p < 0.005). In 36% of the SSc patients, the serum P1CP level was significantly elevated more than two standard deviations above the mean control value. The mean serum P1CP level in patients with diffuse SSc was significantly higher than in those with limited SSc (411 +/- 373 vs 255 +/- 199 ng/ml; p < 0.05). In addition, the SSc patients with elevated serum P1CP levels showed a significantly greater incidence of lung fibrosis and joint involvement than those with normal P1CP levels (p < 0.005 and p < 0.05, respectively). These results suggest that the serum P1CP level is a useful indicator of the severity of disease in SSc patients.