Association of metabolites reflecting type III and VI collagen formation with modified Rodnan skin score in systemic sclerosis - a cross-sectional study.

The objective was to investigate blood-based biomarkers of type I (PRO-C1), III (PRO-C3) and VI (PRO-C6) collagen formation in systemic sclerosis (SSc) patients and examine their correlation to modified Rodnan skin score (mRSS). Limited (lSSc,  = 76) and diffuse SSc (dSSc,  = 41) fulfilling the ACR/EULAR 1980 and 2013 classification criteria for SSc and asymptomatic controls ( = 9) were included. PRO-C1, PRO-C3 and PRO-C6 were measured in serum. LSSc compared to dSSc were significantly older, had longer disease duration and lower mRSS. PRO-C3 was higher in early dSSc compared to early lSSc (mean [95 percentile], 27.4 [13.1-39.1] ng/mL vs 14.9 [8.2-28.8] ng/mL,  = 0.006). PRO-C6 levels were higher in early dSSc compared to early lSSc and late dSSc (early dSSc: 28.2 [10.4-92.3] ng/ml vs early lSSc: 11.0 [6.9-28.5] ng/ml;  = 0.006 and late dSSc: 12.6 [6.5-25.3] ng/mL,  = 0.04). No difference was observed with PRO-C1. PRO-C3 and PRO-C6 were moderately correlated with mRSS with R-partials of 0.36 ( < 0.001) and 0.29 ( = 0.002), respectively Measures of type III and VI collagen formation are potential objective biomarkers of fibrosis in systemic sclerosis. These biomarkers could be useful in monitoring the disease and efficacy of treatment.