Serum surfactant protein D predicts the outcome of patients with idiopathic pulmonary fibrosis treated with pirfenidone.

Background: Idiopathic pulmonary fibrosis (IPF) is a fatal pulmonary disease with poor prognosis. Pirfenidone, the first antifibrotic drug, suppresses the decline in forced vital capacity (FVC) and improves prognosis in some, but not all, patients with IPF; therefore, an indicator for identifying improved outcomes in pirfenidone therapy is desirable. This study aims to clarify whether baseline parameters can be predictors of disease progression and prognosis in patients with IPF treated with pirfenidone.

Methods: We retrospectively investigated patients with IPF who started treatment with pirfenidone between December 2008 and November 2014 at the Sapporo Medical University Hospital. Patients treated with pirfenidone for ≥6 months were enrolled in this study and were observed until November 2015. We investigated the association of clinical characteristics, pulmonary function test results, and blood examination results at the start of pirfenidone with the outcome of patients.

Results: Sixty patients were included in this study. In multivariate logistic regression analysis, % predicted FVC and serum surfactant protein (SP)-D levels were predictors of a ≥10% decline in FVC in the initial 12 months. In the Cox proportional hazards model, these two factors predicted progression-free survival. Pack-years, % predicted diffusing capacity for carbon monoxide, and SP-D levels predicted overall survival.

Conclusions: The serum SP-D level was a predictor of disease progression and prognosis in patients with IPF treated with pirfenidone. In addition, this analysis describes the relative usefulness of other clinical parameters at baseline in estimating the prognosis of patients with IPF who are candidates for pirfenidone therapy.