The diffusing capacity of the lungs for carbon monoxide - an independent predictor of interstitial lung disease in patients with rheumatoid arthritis - results of a prospective study

Abstract

Background. The diffusing capacity of the lungs for carbon monoxide (DLCO) represents the most sensitive independent factor for highlighting the interstitial lung disease associated with rheumatoid arthritis (RA-ILD). Many studies have analyzed this association between RA and lung modifications because it correlates with a decrease in the patients’ quality of life and a higher mortality. Objective. This study aimed to highlight the importance of DLCO as a predictor of ILD progression in RA, beside the pattern on high-resolution chest CT (HRCT) and the double seropositivity of the disease. Patients and method. This prospective cohort study, carried out between august 2022 and may 2023, included 48 RA patients with ILD, fulfilling the 1987 ACR or 2010 ACR/EULAR classification criteria. Important attention was paid to respiratory functional tests, immunological changes, and specific lung pattern on HRCT. Patients with current malignancies, active infections or Overlap syndrome were excluded from the study. Results. 48 RA patients, mostly women (81%) with a mean age of 65.54±10.58 years old and a median age of RA onset of 52.58±11.36 years, were included. The proportion of patients with a decreased DLCO was 64.6%. Using statistical tests, we found significant correlations between DLCO and age, double seropositivity and a specific pulmonary pattern on HRCT. Conclusion. ILD, an underrecognized disease, may be considered one of the most serious of all extra-articular manifestations in RA, the risk for mortality being triple in these cases. Our results are in correlation with the published data and support the key role of DLCO in the diagnosis and follow-up of these patients.