Detection of decline in pulmonary function in patients with systemic sclerosis-associated interstitial lung disease using home monitoring in the Netherlands (DecreaSSc): a prospective, observational study.

Abstract

Background: In patients with systemic sclerosis, interstitial lung disease (ILD) is the leading cause of mortality. Early detection of progressive ILD associated with systemic sclerosis is warranted for timely adjustment of management strategies and improved prognosis. We aimed to investigate the validity of home spirometry to detect a decline in pulmonary function in patients with systemic sclerosis-associated ILD.

Methods: DecreaSSc was a prospective, observational study done in two tertiary referral centres in the Netherlands. Eligible patients were aged 18 years or older, fulfilled the American College of Rheumatology-European Alliance of Associations for Rheumatology criteria for systemic sclerosis, had a disease duration from first non-Raynaud phenomenon symptom of 5 years or less, had high-resolution CT-confirmed diagnosis of ILD, and had a maximum immunosuppressive treatment duration of 8 weeks at baseline. Patients took weekly home spirometry measurements using a handheld spirometer for 1 year. At baseline and at semi-annual study visits, patients pulmonary function testing was done in the hospital and patients completed questionnaires on patient-reported outcome measurements. The primary outcome was the κ agreement between home and hospital measurements after 1 year to detect a decline in force vital capacity (FVC) of 5% or more, estimated using separate linear regression analyses for home-based and hospital-based FVC% predicted in individual patients. The sensitivity and specificity of home spirometry to detect an absolute decline in FVC% predicted of 5% or more was assessed using the hospital pulmonary function test as the gold standard. The longitudinal correlation between hospital and home measurements was assessed with regression analysis, whereas the cross-sectional correlation was assessed with the intraclass coefficient. People with lived experience were involved at several stages of the study.

Findings: Between Jan 26, 2021, and Feb 27, 2023, 43 patients were enrolled, 35 of whom completed 6 months of follow-up and 31 of whom completed 12 months of follow-up. The last follow-up visit took place on March 28, 2024. 20 (57%) of patients were women and 15 (43%) were men; 32 (91%) were White. Mean age was 57·7 years (SD 10·7). The agreement between hospital and home measurements had a κ value of 0·40 (95% CI 0·01-0·79). The sensitivity of home spirometry to detect a decline in FVC% predicted of 5% or more was 60% (95% CI 44-76) and specificity was 87% (75-98). Regression analysis showed that the course of pulmonary function was not different between hospital and home assessment as the interaction term was not significant (-0·0003 [95% CI -0·0006 to 0·000008]; p=0·057) with a longitudinal correlation of 0·55 (95% CI 0·26-0·74; p=0·0070). The intraclass coefficient between both measurements was 0·85 (95% CI 0·73-0·92; p<0·0001) at baseline, 0·84 (0·71-0·92; p<0·0001) at 6 months, and 0·72 (0·50-0·86; p<0·0001) at 12 months.

Interpretation: Home spirometry has the potential to detect a decline in pulmonary function in patients with systemic sclerosis-associated ILD earlier when used in addition to regular health care management. Future research could reveal whether home spirometry can contribute to improved outcomes of patients with systemic sclerosis-associated ILD.

Funding: Galapagos and Boehringer Ingelheim.