Finding the Best Thresholds of FEV1 and Dyspnea to Predict 5-Year Survival in COPD Patients: The COCOMICS Study

Abstract

Background: FEV1 is universally used as a measure of severity in COPD. Current thresholds are based on expert opinion and not on evidence. Objectives: We aimed to identify the best FEV1 (% predicted) and dyspnea (mMRC) thresholds to predict 5-yr survival in COPD patients. Design and Methods: We conducted a patient-based pooled analysis of eleven COPD Spanish cohorts (COCOMICS). Survival analysis, ROC curves, and C-statistics were used to identify and compare the best FEV1 (%) and mMRC scale thresholds that predict 5-yr survival. Results: A total of 3,633 patients (93% men), totaling 15,878 person-yrs. were included, with a mean age 66.469.7, and predicted FEV1 of 53.8% (+/- 19.4%). Overall 975 (28.1%) patients died at 5 years. The best thresholds that spirometrically split the COPD population were: mild >= 70%, moderate 56-69%, severe 36-55%, and very severe <= 35%. Survival at 5 years was 0.89 for patients with FEV1 >= 70 vs. 0.46 in patients with FEV1 <= 35% (H. R: 6; 95% C. I.: 4.69-7.74). The new classification predicts mortality significantly better than dyspnea (mMRC) or FEV1 GOLD and BODE cutoffs (all p<0.001). Prognostic reliability is maintained at 1, 3, 5, and 10 years. In younger patients, survival was similar for FEV1 (%) values between 70% and 100%, whereas in the elderly the relationship between FEV1 (%) and mortality was inversely linear. Conclusions: The best thresholds for 5-yr survival were obtained stratifying FEV1 (%) by >= 70%, 56-69%, 36-55%, and <= 35%. These cutoffs significantly better predict mortality than mMRC or FEV1 (%) GOLD and BODE cutoffs.