Curvilinearity of a Maximum Expiratory Flow-Volume Curve: A Useful Indicator for Assessing Airway Obstruction in Children With Asthma.

BACKGROUND: Lung function parameters are used as signs in the diagnosis and evaluation of asthma; however, their sensitivity and specificity are not ideal. We calculated and combined angle beta with lung function parameters to identify the ideal indicator. OBJECTIVE: We aimed to identify an ideal indicator for evaluating the severity of airway obstruction in children with asthma. METHODS: In total, 151 school-age children diagnosed with asthma were selected as the asthma group, and 106 healthy children were selected as the control group. The subjects were divided into the exacerbation group, chronic persistent group, and clinical remission group. Furthermore, the subjects were classified into mild and moderate groups or severe and critical groups. Angle beta was calculated in each group. A receiver operating characteristic curve analysis was performed to determine the cutoff values of angle beta and lung function parameters that together provided high sensitivity and specificity for airway obstruction evaluation in children with asthma. RESULTS: The mean value of angle beta in the asthma group was significantly smaller than that in the control group (178.18 degrees and 196.72 degrees, respectively, P < .001). More exacerbations or greater severity corresponded to smaller angle beta values (P < .001). The best cutoff value of angle beta was 189.43 degrees, and the area under the receiver operating characteristic curve of angle beta was 0.877, which is greater than the area under the receiver operating characteristic curve of FEV1. forced expiratory flow (FEF) at 75% vital capacity (FEF25%), and FEF at 50% vital capacity (FEF50%), but smaller than the area under the receiver operating characteristic curve of FEF75% and FEV1/FVC%. Interestingly, combining these measures can enhance the sensitivity and specificity in assessing airway obstruction. CONCLUSIONS: Angle beta was a useful indicator for assessing airway obstruction. Furthermore, angle beta combined with FEV1, FEV1/FVC%, FEF25%, FEF50%, and FEF75%, can enhance the sensitivity and specificity of airway obstruction evaluations.