A score without diffusion capacity of the lung for carbon monoxide for estimating survival in idiopathic pulmonary fibrosis

Prediction models for survival at baseline evaluation have been proposed in idiopathic pulmonary fibrosis (IPF) but include diffusion capacity of the lung for carbon monoxide, a test not available in many places. The aim of the present study was to develop a simple new mortality risk scoring system for patients with IPF at initial evaluation without diffusion capacity of the lung for carbon monoxide measurement. A total of 173 patients, 72% males, mean age 70 years, 64% smokers/ex-smokers, were included in a retrospective study. The diagnosis was made by surgical lung biopsy in 40 (23%); in the remaining patients, a usual interstitial pneumonia pattern was present in high-resolution computed tomography. Patients with forced expiratory volume in 1 second/forced vital capacity ratio (FEV(1)/FVC) <0.70 were excluded. Dyspnea was evaluated by magnitude of task on the Mahler scale (Chest 1984). Peripheral oxygen saturation was measured by oximetry at rest and at the end of a 4 minutes step test or a 6-minute walk test. At the end of the follow-up period, 154 (89%) of the patients had died. Based on the univariate Cox proportional-hazards model, survival (P ≤ .10) was related directly to the dyspnea score, presence of cough, lower values of FVC% and FEV(1)%, lower rest and oxygen desaturation during exercise, and greater FEV(1)/FVC. By Cox multivariate analysis, the results remained correlated to the survival dyspnea score, FVC%, and exercise peripheral oxygen saturation. A score, using these variables, was developed and was able to discriminate among 3 groups, with high, low, and intermediate survival curves. A prognostic score, taking into account dyspnea, FVC%, and oxygen desaturation during exercise, can estimate survival in IPF.