Increased type I collagen degradation correlates with disease activity in reactive arthritis

The assay for the cross-linked carboxyterminal telopeptide of type I collagen (ICTP) has been shown to reflect increased type I collagen degradation in patients with rheumatoid arthritis. To look for increased collagen degradation in other inflammatory rheumatic diseases, we studied plasma ICTP in patients with reactive arthritis (ReA).

ICTP was determined by radioimmunoassay from 69 ReA patients. ICTP data on 56 patients aged > or = 20 years were compared with normal ICTP values available for that age group.

The median (range) plasma ICTP concentration of the patients > or = 20 years of age was 3.9 (2.1-9.6) micrograms/l, and in 13 (23%) of them the value was elevated if compared with the normal upper reference limit (mean + 2SD), 5.2 micrograms/l, given by the manufacturer. The mean (SD) duration of joint symptoms was 76 (61) days in patients with ReA. Modest albeit statistically significant correlations were noted between the plasma ICTP and the erythrocyte sedimentation rate, C-reactive protein and the Lansbury articular index (Spearman's r 0.39, 0.37 and 0.29, respectively). The median values for all of the above mentioned parametres were at least twice as high in the group of patients with elevated ICTP compared with those in patients with normal values (p < 0.05). No statistically significant correlation was detected between the plasma ICTP and the duration of joint symptoms.

Increased type I collagen degradation can take place in ReA, and this process seems to correlate with the extent and activity of the joint disease.