Reliability of Portable Spirometry Performed in the Korea National Health and Nutrition Examination Survey Compared to Conventional Spirometry.

Park, Hye Jung; Rhee, Chin Kook; Yoo, Kwang Ha; Park, Yong Bum

Background The Korea National Health and Nutrition Examination Survey (KNHANES) is a well-designed survey to collect national data, which many researchers have used for their studies. In KNHANES, although portable spirometry has been used, its reliability has not been verified. Methods We prospectively enrolled 58 participants from four Korean institutions. The participants were classified into normal pattern, obstructive pattern, and restrictive pattern groups according to their previous spirometry results. Lung function was estimated by conventional spirometry and portable spirometry, and the results were compared. Results Intraclass correlation coefficients (ICCs) of forced vital capacity (FVC) (coefficient, 9.993; 95% confidence interval [CI], 0.988-0.996), forced expiratory volume in 1 s (FEV1) (coefficient, 0.997; 95% CI, 0.995-0.998), FEV1/FVC ratio (coefficient, 0.995; 95% CI, 0.992-0.997), and FEF25-75% (coefficient, 0.991; 95% CI, 0.984-0.994) were excellent (all P<0.001). In the subgroup analysis, the results of the three parameters were similar in all groups. In the overall and subgroup analyses, Pearson's correlation of all the parameters was also excellent in total (coefficient, 0.986-0.994; P<0.001) and in subgroup analysis (coefficient, 0.915-0.995; P<0.001). In the paired t-test, FVC, FEV1/FVC, and FEF25-75% was statistically different between estimated by two instruments. However, FEV1 was not significantly different. Conclusions Lung function estimated by portable spirometry was well-correlated with that estimated by conventional spirometry. Although the value had minimal differences between them, we suggest that the spirometry results from the KNHANES are reliable.