Association of serum biomarkers with pulmonary involvement of rheumatoid arthritis interstitial lung disease: From korail cohort baseline data

Objective. The increase in mortality in rheumatoid arthritis (RA) patients with interstitial lung disease (ILD) is well known. However, there are few studies on serum markers that can evaluate acute exacerbation or prognosis in RA-ILD patients. The purpose of this study was to identify the association between biomarkers and lung lesions in patients with RA-ILD. Methods. We analyzed 153 patients with serum samples in a prospective, multicenter cohort of Korean RA-ILD patients. The serum levels of biomarkers, matrix metalloproteinase (MMP-7), surfactant protein-D (SP-D), and Krebs von den Lungen-6 (KL-6) were measured and correlated with forced vital capacity (FVC), diffusing capacity for carbon monoxide (DLCO) and the results of computed tomography (CT). CT results were interpreted semi-quantitatively according to the extent of lung lesions (grade 1, 0%∼ 25%; grade 2, 26%∼50%; grade 3, 51%∼75%; grade 4, 76%∼100%). Results. MMP-7, SP-D, and KL-6 were negatively correlated with FVC (MMP-7, r=-0.267, p=0.001; SP-D, r=-0.250, p=0.002; KL-6, r=-0.223, p=0.006) and DLCO (MMP-7, r=-0.404, p<0.001; SP-D, r=-0.286, p=0.001; KL-6, r=-0.226, p=0.007). In addition, MMP-7, SP-D, and KL-6 tended to increase with higher grades of lung lesions on CT (MMP-7, p=0.013; SP-D, p<0.001; KL-6, p<0.001). Conclusion. MMP-7, SP-D, and KL-6 can be used to evaluate the functional and anatomical status of lung involvement in the RA-ILD patients.