Prognostic factors for primary Sjögren's syndrome-associated interstitial lung diseases

Interstitial lung disease (ILD) is a condition characterized by a higher mortality rate in primary Sjögren's syndrome (pSS). However, factors influencing the outcome of patients with pSS-associated ILD remain unclear. The aim of the present study was to evaluate predictive factors associated with a worse prognosis in pSS-ILD.

This retrospective study included 99 consecutive patients with pSS-ILD. Clinical characteristics, laboratory findings, and pulmonary function tests at the time of diagnosis were analyzed. Chest HRCT images were reviewed by two experienced chest radiologists. Prognostic factors were assessed by univariate and multivariate analyses, using Cox proportional hazards regression model.

Median age was 68 years (73% women). In the total patient population, the 5- and 10-year survival rates were 89.8% and 79.0%, respectively. Univariate analysis revealed a significant association between prognosis and age, serum Krebs von den Lungen-6 (KL-6) levels, and %FVC. None of the chest HRCT findings were related to patient outcomes. Based on multivariate analyses adjusted by age and gender, lower levels of %FVC and higher levels of KL-6 were significantly associated with poor outcomes. Using optimal cutoff levels, according to receiver operating characteristic curve analyses, KL-6 > 800 U/mL were significantly associated with worse prognosis (HR: 2.91, 95% CI: 1.04-8.10). Patients with elevated serum KL-6 levels (>800 U/mL) showed a higher mortality rate than those without elevated serum KL-6 levels (p = 0.02).

Lower %FVC and higher serum KL-6 levels are predictive factors for poor outcome in patients with pSS-ILD.