Combining spirometry and fractional exhaled nitric oxide improves diagnostic accuracy for childhood asthma

Objectives There are insufficient evidences supporting the use of spirometric indices along with tests for airway inflammation to improve diagnostic accuracy for asthma. We aimed to study the utility of combination of spirometric indices and fractional exhaled nitric oxide (FeNO) measured at the initial visit in diagnosing asthma. Methods Consecutive children aged 8‐16 years who were referred for evaluation of possible asthma were included. At referral, all participants completed FeNO measurements and spirometry. The diagnosis of asthma was established with conventional criteria. Diagnostic performance of the spirometric indices and FeNO was determined using receiver‐operator characteristic (ROC) curve analyses. Results Of 275 participants, 191 children were diagnosed with asthma and showed lower spirometric indices and higher FeNO than non‐asthmatics. In the ROC curve analyses, forced expiratory flow between 25% and 75% of vital capacity (FEF25‐75) percent predicted demonstrated diagnostic performance with the area under the ROC curve (AUC) value of 0.81 (95% CI: 0.76‐0.87) which was significantly higher than those for forced expiratory volume in the first second (FEV1) percent predicted and FEV1/forced vital capacity. The combined use of FEF25‐75 percent predicted and FeNO improved the AUC to 0.90 (95% CI: 0.86‐0.93). In addition, compared to FEF25‐75 percent predicted or FeNO alone, this combination improved sensitivity with comparable specificity. Conclusions FEF25‐75 percent predicted had a better diagnostic value in detection of childhood asthma than other standard spirometric indices and its combination with FeNO improves the diagnostic accuracy for childhood asthma.