Prognostic value and predictors of the alteration of the diffusing capacity of the lungs for carbon monoxide in systemic lupus erythematosus

Abstract Objectives SLE is a systemic autoimmune disease characterized by heterogeneous manifestations and severity, with frequent lung involvement. Among pulmonary function tests, the measure of the diffusing capacity of the lungs for carbon monoxide (DLCO) is a noninvasive and sensitive tool assessing pulmonary microcirculation. Asymptomatic and isolated DLCO alteration has frequently been reported in SLE, but its clinical relevance has not been established. Methods This retrospective study focused on 232 SLE patients fulfilling the 2019 EULAR/ACR classification criteria for SLE. Data were collected from the patient’s medical record, including demographic, clinical and immunological characteristics, while DLCO was measured when performing pulmonary function tests as part of routine patient follow-up. Results At the end of follow-up, DLCO alteration (<70% of predicted value) was measured at least once in 154 patients (66.4%), and was associated with a history of smoking as well as interstitial lung disease, but was also associated with renal and neurological involvement. History of smoking, detection of anti-nucleosome autoantibodies and clinical lymphadenopathy at diagnosis were independent predictors of DLCO alteration, while early cutaneous involvement with photosensitivity was a protective factor. DLCO alteration, at baseline or any time during follow-up, was predictive of admission in intensive care unit and/or of all-cause death, both mainly due to severe disease flares and premature cardiovascular complications. Conclusion This study suggests a link between DLCO alteration and disease damage, potentially related to SLE vasculopathy, and a prognostic value of DLCO on death or intensive care unit admission in SLE.