The role of inflammatory markers in assessment of disease activity in systemic sclerosis

Objective: The role of the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) in the assessment of disease activity in systemic sclerosis (SSc) remains controversial. We sought to evaluate the relationship between clinical features of SSc and raised inflammatory markers and to determine if changes in ESR and CRP reflect changes in other disease features over time. Methods: One thousand, five hundred and forty-five patients enrolled in the Australian Scleroderma Cohort Study were observed over a mean 3.52±2.91 years and assessed at 6,119 study visits. Generalised estimating equations were used to determine the relationship between ESR≥20mm/hr and CRP≥5mg/L and features of disease. The associations between change in inflammatory markers and change in skin scores and respiratory function tests were analysed. Results: Overall, there was a significant association between raised ESR and forced vital capacity (FVC)<80% predicted, diffusing capacity of the lung (DLCO)<80% predicted, pulmonary arterial hypertension (PAH), body mass index (BMI), proximal muscle strength, anaemia, and hypocomplementaemia (p<0.05). Raised CRP was significantly associated with modified Rodnan Skin Score>20, FVC<80%, DLCO<80%, PAH, digital ulcers, BMI, synovitis, tendon friction rub, anaemia, and hypocomplementaemia (p<0.05). A significant deterioration in respiratory function tests (RFTs) was associated with a 2-fold increase in both ESR and CRP (p<0.05). Conclusion: Raised inflammatory markers are associated with pulmonary, cutaneous and musculoskeletal manifestations of SSc. Rising inflammatory markers are correlated with declining respiratory function tests. This suggests inflammatory markers have a role in the assessment of SSc disease activity.