Background and objective Post-bronchodilator (BD) lung function is recommended for diagnosing COPD. However, often only pre-BD lung function is used in clinical practice or epidemiological studies. We aimed to compare the discrimination ability of pre-BD and post-BD lung function to predict all-cause mortality. Methods Participants aged ≥40 years with airflow limitation (N=2538) and COPD (N=1262) in HUNT2 (1995-1997) were followed until December 31, 2015. Survival analysis and time-dependent area under receiver operating characteristics curves (AUCs) were used to compare the discrimination ability of pre-BD and post-BD lung function (percent-predicted FEV1 (ppFEV1), FEV1 z-score, FEV1Q, modified-GOLD categories, or GOLD grades). Results Among 2538 participants, 1387 died. The AUCs for pre-BD and post-BD ppFEV1 to predict mortality were 60.8 and 61.8 (p=0.005), respectively, at 20 years’ follow-up. The corresponding AUCs for FEV1 z-score were 58.5 and 60.4 (p<0.001), for FEV1Q were 68.7 and 70.1 (p=0.002), and for modified-GOLD categories were 62.3 and 64.5 (p<0.001). Among participants with COPD, the AUCs for pre-BD and post-BD ppFEV1 were 57.0 and 58.8 (p<0.001), respectively. The corresponding AUCs for FEV1 z-score were 53.1 and 55.8 (p<0.001), for FEV1Q were 63.6 and 65.1 (p=0.037), and for GOLD grades were 56.0 and 57.0 (p=0.268). Conclusions Mortality was better predicted by post-BD than by pre-BD lung function, however, they differ only by a small margin. The discrimination ability using GOLD grades among COPD participants was similar.
- area under the curve