A Cross-sectional Study of Pulmonary Function among Patients of Rheumatoid Arthritis on Low-dose Methotrexate by Spirometry

Abstract Objective: Rheumatoid arthritis (RA) is characterized by persistent synovitis with systemic inflammation, primarily affecting the bilaterally symmetrical joints of the hands and feet. It has also been associated with the development of interstitial lung disease as the disease progresses. Disease-modifying antirheumatic drugs (DMARDs) have been key therapeutic agents, with methotrexate (MTX) commonly administered weekly in low doses. MTX has also been linked to hypersensitivity pneumonitis and the progression of pulmonary complications in RA, potentially contributing to a decline in lung function. This study was planned to estimate spirometry parameters to assess pulmonary function in RA patients receiving chronic low-dose oral MTX therapy. Materials and Methods: A total of 71 patients of the age group 20–60 years were included in the study. Spirometry parameters (forced expiratory volume in 1 s [FEV 1 ], forced vital capacity [FVC], FEV 1 /FVC) were estimated using COSMED spirometer with the help of computer software after taking relevant medical history and anthropometric parameters (height and weight). Evaluation was done using American Thoracic Society (ATS) guidelines for spirometry. Pearson’s correlation coefficient was used to correlate the means and predicted percentages of estimated parameters. Results: 49.29% of patients had an outcome of possible restriction, 5.6% had a possible mixed type, 1.4% had obstructive component, and 43.6% had normal outcomes on spirometry. There was a strong negative correlation between FVC predicted percentage ( r = −0.569, p < 0.001) and FEV 1 predicted percentage ( r = −0.604, p < 0.001) with the disease duration. A strong negative correlation between FEV 1 predicted percentage ( r = −0.600, p < 0.001) and FVC predicted percentage ( r = −0.650, p < 0.001) with duration of treatment. Conclusion: Our study noted a decline in lung function parameters (FEV 1 , FVC, and FEV 1 /FVC) in RA patients on low-dose MTX, with a strong negative correlation to disease and treatment duration. Further assessments using DLCO, plethysmography, or high-resolution computed tomography and also assessment of other confounding factors like smoking are needed to clarify MTX’s role in lung function decline.