Comparative analysis of connective tissue disease–associated interstitial lung disease and interstitial pneumonia with autoimmune features

Objective This retrospective clinical study aimed to examine the similarities and differences between connective tissue disease–associated interstitial lung disease (CTD-ILD) and interstitial pneumonia with autoimmune features (IPAF) and to identify the influencing factors of CTD-ILD, with a goal of early detection and active treatment of the disease. Methods We conducted a retrospective study of 480 patients: 412 with CTD-ILD and 68 with IPAF. Demographic features, clinical characteristics, laboratory indicators, and chest high-resolution computed tomography (HRCT) imaging data were analyzed. Results Compared with the IPAF group, the CTD-ILD group contained more women, and the incidences of joint pain, dry mouth/dry eyes, and Raynaud’s phenomenon were higher; erythrocyte sedimentation rate (ESR) and D-dimer levels were higher; red blood cell (RBC) and hemoglobin (Hb) levels were lower; a high rheumatoid factor (RF) titer (> 2 times the normal upper limit) was observed, and anti-cyclic citrullinated peptide antibody (anti-CCP), anti-keratin antibody (AKA), antinuclear antibody (ANA), and anti-melanoma differentiation-associated gene 5 antibody (anti-MDA5) levels were higher. Compared with CTD-ILD patients, IPAF patients were more likely to present initially with respiratory symptoms, with higher rates of fever, cough and expectoration, dyspnea, and Velcro crackles; anti-Ro52 titers were higher; incidences of honeycombing opacity, reticulate opacity, patchy opacity, and pleural thickening were greater. Female sex, a high RF titer (> 2 times the normal upper limit), anti-CCP positivity, ANA positivity, and anti-MDA5 positivity were risk factors for CTD-ILD when the odds ratios were adjusted. Conclusion CTD-ILD and IPAF patients differed in demographic features, clinical characteristics, laboratory indicators, and chest HRCT imaging data. Female sex, a high RF titer (> 2 times the normal upper limit), anti-CCP positivity, ANA positivity, and anti-MDA5 positivity were risk factors for CTD-ILD. Key Points • This retrospective clinical study comprehensively compared the demographic features, clinical characteristics, laboratory indicators, and chest HRCT imaging data of CTD-ILD and IPAF patients . • The evidence suggested that female sex, a high RF titer, anti-CCP positivity, ANA positivity, and anti-MDA5 positivity were risk factors for CTD-ILD .