Comparison of new spirometry measures to diagnose Chronic Obstructive Pulmonary Disease : A diagnostic test study

Abstract

Background and Objective Chronic Obstructive Pulmonary Disease (COPD) is diagnosed using the FEV1/FVC, which has limitations as a diagnostic test. We assessed the validity of several measures derived from the expiratory phase of the flow-volume curve obtained from spirometry to diagnose COPD: the slopes corresponding to the volume expired after the 50% and 75% of the FVC, the slope formed between the Peak Expiratory Flow (PEF) and the FVC, and the area under the expiratory flow/volume curve. Methods We conducted a cross-sectional diagnostic test study in 765 consecutive patients referred to spirometry because of respiratory symptoms. We compared the reproducibility and accuracy of the proposed measures against FEV1/FVC post-bronchodilator <0.70. We evaluated the proportion of respiratory symptoms for both the FEV1/FVC and FEV1/FEV6 ratios, and the PEF slope. Results Subjects had a mean age of 65.8, 57% were women, and 35% had COPD. The test-retest intraclass correlation coefficient for FEV1/FVC was 0.89, it was 0.85 for FEV1/FV6 was, for the PEF slope was 0.83, for the area under the expiratory flow/volume curve was 0.93, for the area under the potential expiratory flow/volume curve was 0.96, for the area under the potential expiratory flow/volume of at 75% of the FVC 0.97, and for the slope at 50% of the FVC was 0.82. The area under-the-ROC curve was 0.99 for FEV1/ FEV6, 0.99 for the slope at 50% of the FVC, and 0.98 for the PEF slope.