Introduction C reactive protein (CRP) is an acute-phase protein synthesised in response to tissue damage or inflammation. Previous studies evaluating the role of CRP in sarcoidosis have focussed on disease monitoring. Adequate markers to determine predictors of progression in sarcoidosis are currently lacking.
Objectives The aim of this retrospective observational study is to evaluate the utility and practical application of baseline serum CRP in predicting treatment indication and disease severity in a well-defined sarcoidosis population over a 26-year follow-up period.
Methods We reviewed the clinical, biochemical, radiological and physiological findings in all confirmed sarcoidosis patients attending a regional referral centre between 1983 and 2009. Disease progression was defined in two ways: decline in lung function as per Hunninghake criteria (>15% reduction in baseline FEV1 % and/or >10% decline in baseline DLCO%); and radiological progression (defined as worsening stage of disease and/or development of bronchiectasis or cavitation). Indication for treatment was defined as need for corticosteroid treatment throughout duration of follow-up. Correlation coefficients and multiple logistic regression (MLR) analysis were performed to determine independent baseline variables relating to outcome. Results are expressed as OR, 95%-CIs and p-values.
Results 328/409 (80.2%) of sarcoidosis patients were suitable for inclusion, 46.6% of whom had an abnormally elevated CRP at presentation. MLR analysis of presenting characteristics with baseline CRP showed strong associations with Löfgren's syndrome (p=0.002) and FVC % (p=0.009), consistent with previously published data. In terms of predicting outcomes, CRP was found to be an independent predictor of both radiological progression and physiological deterioration (p=0.026 and 0.048 respectively). Other independent indices for radiological progression were smoking status, Löfgren's syndrome and Scadding CXR stage at presentation (p=0.035, 0.002 and <0.001 respectively). DLCO % was shown to be a further independent predictor of physiological decline (p=0.015).
Conclusion This is one of the largest clinical studies investigating the predictive influence of CRP in sarcoidosis. The data suggests a role for CRP as a predictive indicator of physiological deterioration and radiological progression. Therefore, a subset of chronic sarcoidosis patients with high baseline CRP at presentation may benefit from closer monitoring and extra attention to parameters of physiological and radiological decline.
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