Abstract
Background: Chronic obstructive pulmonary disease (COPD) is a frequent but underdiagnosed disease, primarily due to the lack of access to forced spirometry (FS) in primary care. Portable, easy-to-use expiratory flow meters like Piko-6(®) and COPD-6(®) that measure FEV(1), FEV(6), and FEV(1)/FEV(6) ratio provide an alternative. Given that Piko-6(®) and COPD-6(®) devices measure FEV(6) but not FVC, the aim of the study is to determine the optimal cutoff value for the FEV(1)/FEV(6) ratio of each device to avoid false negatives when these devices are used for COPD screening in primary care (PC). Methods: A total of 664 patients of 35 years of age or older with a cumulative tobacco consumption of 10 or more packs/year were recruited at two university hospitals. FS (gold standard) was performed and FEV(1), FVC, and FEV(1)/FVC measurements were compared with FEV(1), FEV(6), and FEV(1)/FEV(6) measurements acquired using Piko-6(®) and COPD-6(®) devices. The devices were compared using statistical methods including Pearson correlation coefficients, the Youden index (YI), kappa coefficient, Bland-Altman plots, and ROC curves analysis. Results: Correlations between FEV(1)/FEV(6) using Piko-6(®) and COPD-6(®) and FEV(1)/FVC with FS were 0.79 and 0.73, respectively. Piko-6(®) achieved the best YI in FEV(1)/FEV(6) (0.73), whereas for COPD-6(®), it was 0.80. Concordance between Piko-6(®) and FS was 83.9% (kappa 0.67 ± 0.028) and for COPD-6(®), it was 68.7% (kappa 0.42 ± 0.02). Conclusions: This is the first study that compares two hand-held expiratory flow meters with FS. Piko-6(®) and COPD-6(®) devices are effective tools for COPD detection, as their measurements provide a good correlation with FS. In order to avoid false negative results, the FEV(1)/FEV(6) cutoff point needs to be increased to 0.73 and 0.80 with Piko-6(®) and COPD-6(®), respectively.