[Assessment of the portable COPD-6 device for detecting obstructive airway diseases]

To evaluate the agreement and the association with FEV(1), FEV(6) and FEV(1)/FEV(6) measured with the Vitalograph-COPD-6 portable device and the FEV(1), FVC and FEV(1)/FVC by conventional spirometry, and to analyse the validity of this device to detect obstruction.

A cross-sectional, descriptive, prospective study, that included 180 subjects. A conventional spirometry and one with the Vitalograph-COPD-6 were sequentially performed on them. The agreement was analysed [kappa index and interclass correlation coefficient (ICC)], as well as the association [Pearson correlation coefficient (r)], area under the ROC curve (AUC) of the FEV(1)/FEV(6) in detecting obstruction, and the sensitivity, specificity, predictive values (PPV and NPV), and probability ratios (PR+ and PR-) of the different FEV(1)/FEV(6) cut-off points in the detection of obstruction.

The prevalence of obstruction was 47%. The kappa index was 0.59 when an FEV(1)/FEV(6) < cut-off point of <0.7 was used. The ICC and the r between the FEV(1) measured by the two instruments, FEV(6) and FEV(1)/FEV(6) measured by the Vitalograph-COPD-6 and the FVC and FEV(1)/FVC determined by the spirometer were all greater than 0.92. The ROC AUC was 0.97. To detect obstruction, if the cut-off point of FEV(1)/FEV(6) (for COPD-6) was <0.70, the sensitivity, specificity, PPV, NPV, CR+ and CR- were, 58%, 100%, 100%, 73%, infinity and 0.42, respectively. For a cut-off point of <0.8, they were 96%, 76%, 78%, 96%, 3.8 and 0.05, respectively.

The portable Vitalograph-COPD6 device is precise for the detection of airway obstruction. The best sensitivity/specificity of FEV(1)/FEV(6) was obtained with cut-off points greater than 0.7.