Association of C-reactive protein with high disease activity in systemic sclerosis: results from the Canadian Scleroderma Research Group

Abstract

Objective: This study was performed to determine the prevalence of elevated C-reactive protein (CRP) levels and the significance of CRP in clinical parameters in systemic sclerosis (SSc; scleroderma) patients.

Methods: Canadian Scleroderma Research Group data were used. Statistical comparisons were made for CRP levels ≤8 mg/liter versus >8 mg/liter, early (≤3 years from first non-Raynaud's phenomenon symptom) versus late SSc, and diffuse cutaneous SSc (dcSSc) versus limited cutaneous SSc (lcSSc). A survival analysis was analyzed between patients with normal versus elevated CRP levels.

Results: A total of 1,043 patients (mean ± SD age 55.4 ± 12.1 years, mean ± SD disease duration of 11.0 ± 9.5 years) were analyzed; elevation of CRP level and erythrocyte sedimentation rate (ESR; >20 mm/hour) occurred in 25.7% and 38.2%, respectively. Mean ± SD baseline CRP level in dcSSc (11.98 ± 25.41 mg/liter) was higher than in lcSSc (8.15 ± 16.09 mg/liter; P = 0.016). SSc patients with an early disease duration had a higher mean ± SD CRP level (12.89 ± 28.13 mg/liter) than those with a late disease duration (8.60 ± 17.06 mg/liter; P = 0.041). Although not consistent in all subsets, CRP was significantly associated (P < 0.01) with ESR, modified Rodnan skin score (MRSS), worse pulmonary function parameters, disease activity, damage, and Health Assessment Questionnaire. CRP level seemed to normalize in many SSc patients over time. Total lung capacity <80% predicted, MRSS, and serum creatinine were predictors of elevated CRP levels in SSc (odds ratio [OR] 2.76 [95% confidence interval (95% CI) 1.73-4.40], P = 0.0001; OR 1.03 [95% CI 1.01-1.05], P = 0.005; and OR 1.005 [95% CI 1.001-1.010], P = 0.02, respectively). Survival for patients with elevated CRP levels was less than for patients with normal CRP levels (P = 0.001).

Conclusion: CRP level is elevated in one-quarter of SSc patients, especially early disease. It is correlated with disease activity, severity, poor pulmonary function, and shorter survival.