Pulmonary function test abnormalities in patients with rheumatoid arthritis: A single centre study

Introduction: Pulmonary diseases are common extra-articular manifestations of rheumatoid arthritis (RA) and account for a high disease-related mortality. Pulmonary function tests (PFTs) are considered as one of the cost-effective options for the early identification of pulmonary involvement in RA. The objective of this study was to assess the prevalence of PFT abnormalities and its associated factors among diagnosed patients with RA visiting a tertiary care hospital in Sri Lanka.
Methods: A cross-sectional study was performed recruiting 42 consecutive RA patients attending the rheumatology clinic of Teaching Hospital Karapitiya, Galle, Sri Lanka (THK) in year 2018-2019. Data were collected using an interviewer-administered questionnaire. Lung functions were measured using spirometry. Mann-Whitney U test, the Spearman rank-order correlation coefficient and the Kruskal Wallis H test at 0.05 significance level were used to identify associations between variables.
Results: Out of all the patients (N = 42), 57.1% showed abnormal PFT results. Among them obstructive defect was noted in 16.6%, small airway defect in 37.5% and pure restrictive defect in 45.9%. No patients with combined restrictive and obstructive diseases were detected. A statistically significant association of forced vital capacity (FVC) with the presence of respiratory symptoms (p = 0.02) was detected. Statistically significant negative correlations were reported between peak expiratory rate (PFR) and age (r_s = -0.371, p = 0.01) and PFR and disease activity (r_s = -0.393, p = 0.01). Age, disease duration, disease severity and presence of  respiratory symptoms showed no association with types of respiratory abnormalities.
Conclusions: PFT abnormalities were detected in considerable proportion of RA patients. PFTs should be performed in patients with RA, irrespective of the duration and the severity of disease or respiratory symptoms.