Pulmonary Function Decline in Very Early Diagnosis of Systemic Sclerosis: A Retrospective Longitudinal Single-Center Study.

OBJECTIVE

The very early diagnosis of systemic sclerosis (SSc; VEDOSS) criteria aim to identify patients at risk of evolving into SSc. The predictive value of diffusing capacity of the lungs for carbon monoxide (DLco) and forced vital capacity (FVC) remains poorly characterized. This study aimed to evaluate whether baseline pulmonary function test (PFT) alterations, especially DLco, predict progression to SSc and to examine longitudinal PFT changes in patients with stable VEDOSS over time.

METHODS

A retrospective longitudinal study was conducted including 73 patients with VEDOSS. Patients were stratified by serologic, capillaroscopic, and clinical features. Annual PFT follow-up was performed at our center. Progression to SSc was defined according to the 2013 American College of Rheumatology/EULAR criteria. Kaplan-Meier curves were generated to evaluate progression rates according to baseline DLco/single breath (SB)%, using 70% as cutoff, and to evaluate time-dependent survival of both DLco% and FVC% decline according to the presence or the absence of SSc-specific antibodies (SSc-Ab), active-late nailfold videocapillaroscopic (NVC) patterns, and puffy fingers. A Cox proportional hazards regression model was used to assess the independent association between baseline DLco/SB (%) and progression-free survival, adjusting for SSc-Ab+, NVC patterns, and the presence of puffy fingers.

RESULTS

Over a median follow-up of five years (maximum 11 years), 12% of patients transitioned to SSc. All progressors were SSc-Ab+ and had lower baseline DLco/SB% values (68.2% vs 81.2%, P = 0.004). A DLco/SB <70% was strongly associated with increased risk of progression toward SSc over time (7.7 vs 10.2 years, log-rank = 0.007). In patients with stable VEDOSS, the time-dependent decline of DLco/SB% was shorter in SSc-Ab+ group (8 vs 10.4 years, log-rank = 0.032). FVC% also declined in the cohort without any influence of disease-specific variables. Cox regression showed that the SSc-Ab+ and scleroderma NVC pattern were the main contributors to progression toward definite SSc.

CONCLUSION

Baseline DLco/SB <70% is a potential marker of disease progression in VEDOSS; however, subtle progressive pulmonary function decline may occur even in stable patients.