Long-term functional course of Sjögren's disease-associated interstitial lung disease.

Background: Interstitial lung disease (ILD) is common in primary Sjögren's disease (pSD); its functional course is poorly known. Our aim was to characterise the long-term functional course and prognosis in patients with pSD-ILD. We determined the role of baseline demographic and clinical variables in the evolution of lung function and identified risk factors for death or transplantation.

Methods: In a retrospective observational cohort study, patients with pSD and ILD were retrospectively identified from two French ILD centres. Forced vital capacity (FVC) and diffusing capacity of the lungs for carbon monoxide (D _LCO) slopes were obtained from joint models. Latent class mixed models identified clusters of FVC and D _LCO trajectories.

Results: We included 73 patients (63% women, mean age 63 years), with a median follow-up of 9.3 years. At baseline, mean FVC was 73±21% and D _LCO 51±16%. On average, FVC was stable, while there was an annual decline in D _LCO of 1% of the predicted value. Male sex, a pattern of usual interstitial pneumonia (UIP) or indeterminate for UIP on high-resolution computed tomography (HRCT), and features of fibrosis on HRCT, were associated with an accelerated decline in FVC and D _LCO.

Conclusion: We identified clusters of lung function evolution. 1) Two FVC trajectories: patients with stable FVC (n=56, 78%); patients with FVC decline (n=16, 22%) of 2.4% per year, characterised by a low baseline D _LCO (39%) and a higher risk of death or transplantation (HR 52, 95% CI 10-273). 2) Three D _LCO trajectories: patients with stable D _LCO (n=44, 66%); patients with a slow decline in D _LCO (n=12, 18%) of 2.8% per year; patients with a rapid decline in D _LCO (n=11, 16%) of 4.8% per year, characterised by a low baseline D _LCO (41%) and a higher risk of death or transplantation (HR 156, 95% CI 18-1352).