Surfactant protein A predicts survival in idiopathic pulmonary fibrosis

Abstract

The purpose of this study was to determine if the measurement of surfactant protein A (SP-A) in bronchoalveolar lavage (BAL) fluid predicts survival in patients with idiopathic pulmonary fibrosis (IPF). We performed BAL on 44 patients with IPF and 33 healthy volunteers. SP-A and total phospholipid (PL) were measured in the surfactant pelleted by centrifugation and expressed as a ratio to account for differences in the alveolar surface area sampled. The mean SP-A/PL was lower in patients with IPF than in healthy volunteers (31.8 +/- 2.8 versus 63.9 +/- 6.4 micrograms/mumol, p = 0.006) and in patients who died within 2 yr than in those who survived (23.4 +/- 2.6 versus 37.5 +/- 4.2 micrograms/mumol, p = 0.015). Using Cox's proportional hazard model, we found that SP-A/PL modeled continuously was associated with survival time (p = 0.002). The 5-yr survival of patients with SP-A/PL above the median level for all patients with IPF (29.7 micrograms/mumol) was more than twice that of patients below the median (68 versus 30%, p = 0.007). SP-A/PL improved upon prediction of survival modeled by most routine physiologic variables with the exception of percent predicted TLC or the multifarious clinical-radiographic-physiologic score (CRP). Cellular analysis of lavage did not predict survival in this cohort of patients. We conclude that SP-A/PL is a biochemical marker in lavage that predicts survival in patients with IPF.