Validation of "lung age" measured by spirometry and handy electronic FEV1/FEV6 meter in pulmonary diseases

The concept of "lung age" is thought to be useful for understanding pulmonary function. In this study, we validated "lung age" to detect pulmonary function abnormalities in pulmonary diseases.

We used both spirometry and an electronic FEV(1)/FEV(6) meter (FEV(6) meter) to perform pulmonary function tests. We evaluated the sensitivity and specificity of FEV(6) and FEV(1)/FEV(6), and calculated "lung age" in Japanese subjects including those with chronic obstructive pulmonary disease (COPD), bronchial asthma (BA), and interstitial lung diseases (ILD).

FEV(1) (spirometer) vs. FEV(1) (FEV(6) meter), FVC (spirometer) vs. FEV(6) (FEV(6) meter), and FEV(1)/FVC (spirometer) vs. FEV(1)/FEV(6) (FEV(6) meter) measurements were all significantly and closely correlated. For the difference of "lung age" and "actual age", the area under the receiver operating characteristic curve (ROC-AUC) for detecting obstructive impairment was 0.807 (spirometer) and 0.772 (FEV(6) meter), respectively. The corresponding ROC-AUC for detecting restrictive impairment was 0.891 and 0.836, respectively, and that for detecting both obstructive and restrictive impairment was 0.918 and 0.853, respectively. For detection of both obstructive and restrictive impairment, the difference of the "lung age" and "actual age" cut-off value, corresponding to the greatest sum of sensitivity and specificity, was 18.3 years (spirometer) and 19.8 years (FEV(6) meter), respectively. The sensitivity was 0.783 (spirometer) and 0.801 (FEV(6) meter), and the specificity was 0.895 (spirometer) and 0.790 (FEV(6) meter), respectively.

"Lung age" can provide an easy interpretation of the results, and can detect pulmonary function abnormalities in pulmonary diseases.