Prognostic Factors in Interstitial Lung Disease Associated with Primary Sjögren’s Syndrome: A Retrospective Analysis of 33 Pathologically–Proven Cases

INTRODUCTION: Interstitial lung disease associated with primary Sjögren’s syndrome (pSS–ILD) shows several patterns such as nonspecific interstitial pneumonia (NSIP) and usual interstitial pneumonia (UIP). Although UIP is a well–recognized prognostic determinant in idiopathic interstitial pneumonias, whether this is also the case in pSS–ILD is unclear. The objectives of this study were to evaluate the prognostic effect of UIP, and to identify the prognostic factors in pSS–ILD. METHODS: A retrospective review of medical records identified 33 consecutive patients with pathologically–proven pSS–ILD. Each patient was classified into each ILD pattern by multidisciplinary analysis. Baseline clinical–radiologic–pathologic characteristics and survival rates were compared between the ILD patterns. Finally, the prognostic factors in pSS–ILD were assessed by univariate and subsequent multivariate analyses using Cox’s proportional hazards regression model. RESULTS: pSS–ILD patients were diagnosed with NSIP (n = 22) or UIP (n = 11). The median follow–up period was 110 months, and five-year survival rate was 87.3% in the total patient population. The prognosis of the UIP patients was not significantly different from that of the NSIP patients (NSIP to UIP, hazard ratio [HR]: 0.77, 95% confidence interval [CI]: 0.18–3.36, P = 0.73). Multivariate analysis identified PaCO(2) (HR: 1.68 per 1 Torr increase, 95% CI: 1.24–2.28, P < 0.01), extent of reticular abnormality on high–resolution CT (HR: 4.17 per 1-grade increment, 95% CI: 1.18–14.73, P = 0.03), and severity of fibroblastic foci (HR: 9.26 per 1-grade increment, 95% CI: 1.74–49.35, P < 0.01) as prognostic factors in pSS–ILD. CONCLUSIONS: UIP in pSS–ILD was not related to poorer prognosis than NSIP. Assessment of detailed clinical–radiologic–pathologic findings is more important than distinguishing UIP to evaluate prognosis in this disease.