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The diagnostic value of angle β in school-aged children with asthma is unknown. We speculate that angle β may reflect diversification of the forced expiratory flow (FEF) to some extent. The objective of this study was to assess the diagnostic accuracy of angle β, FeNO, pulmonary function parameters and their combinations for asthma in school-aged children. In total, 248 children participated in this study (140 children with asthma and 108 healthy children). The diagnostic performance of angle β, FeNO and pulmonary function parameters was determined using receiver operating characteristic (ROC) curves. In the ROC analysis, we used the hold out cross-validation method to avoid overfitting. This study was performed in China and followed the Guidelines for the diagnosis and optimal management of asthma in children (China). 1) In the asthma group, the mean angle β value was significantly smaller than that in the control group (P < 0.001), but the mean FeNO value was significantly higher than that in the control group (P < 0.001). 2) More acute exacerbation or greater severity corresponded to a smaller angle β. 3) Among the single indices, the area under the ROC curve of angle β was the largest (except for FEV1/FVC%). For combined indicators, after cross-verification, the combination of angle β, FEV1/FVC% and FeNO showed the highest diagnostic accuracy. Angle β combined with FeNO and FEV1/FVC% can improve the diagnostic accuracy for asthma in school-aged children. [ABSTRACT FROM AUTHOR]

BACKGROUND: FEV6 can be used as a convenient alternative to FVC. The aim of this study was to determine an alternative to the fixed cutoff points of FEV1VC <0.70 suitable for FEV1/FEV6 in primary care. METHODS: Pulmonary function testing was conducted on volunteers recruited from 4 community centers in Xi'an, China, between July and August 2012. Participants underwent 3 FVC maneuvers. The maneuver with the best FEV1 was retained. FVC, FEV1 and FEV6 were measured by portable spirometer. The receiver operating characteristic curves that corresponded to the optimal combination of sensitivity and specificity for FEV1/FEV6 were determined. A kappa test was used to compare the agreement between FEV1FVC and FEV1/FEV6. The positive predictive value and negative predictive value were also calculated. RESULTS: A total of 767 volunteers participated in this study, of whom 297 were male and 470 were female. Considering FEV1/FVC <0.70 as the accepted standard for COPD, the area under the curve was 98% (P < .001), and the FEV1/FEV6 cutoff, corresponding to the greatest sum of sensitivity and specificity, was 0.72. For the total population, the FEV1/FEV6 sensitivity, specificity, positive predictive value, and negative predictive value were 96.9, 98.8, 95.8, and 99.2%, respectively. The agreement between the 2 cutoff points was excellent, and the kappa value was 0.954. CONCLUSIONS: FEV1/FEV6 <0.72 can be used in primary care as a valid alternative to FEV1/FVC <0.70 as a fixed cutoff point for the detection of COPD in adults. This study suggests that FEV1FEV6 is an effective and well validated option that should be used in primary care to detect COPD, which is a rampant problem. [ABSTRACT FROM AUTHOR]