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Exhaled nitric oxide can't replace the methacholine challenge in suspected pediatric asthma
Anja Keßler1, Uwe Kragl2, Änne Glass3
1Department of Pediatrics, Rostock University Medical Hospital, Rostock, Germany; Private Practice for Pediatric Pulmology and Allergology, Neubrandenburg, Germany.
Background:
In adults, measurement of FENO has been recently suggested as a substitute for the methacholine challenge test (MCT) for diagnosis of asthma. This study aimed to evaluate whether FeNO is a substitute for MCH also in children with suspicious asthma.
Methods:
During a single visit steroid naive children (5-17 years) with suspicious asthma underwent skin prick test (SPT), FENO measurement and spirometry prior and during MCT (one concentration procedure). Results of the SPT (atopy/non-atopy) and MCT (asthma/non-asthma) were used for categorization. ROC analysis in atopy non-atopy subgroups yielded sensitivity, specificity, positive and negative predictive value (PPV and NPV) for FENO.
Results:
The SPT revealed atopy in 134 out of 222 children (age 9.7 ± 3.2 years) investigated and asthma was diagnosed in 114 (77/37 atopy/non-atopy) patients. FENO values in patients with atopic asthma were significantly higher compared to those with either non-atopic asthma or atopia without asthma (18 ppb (5-89) vs 7 ppb (5-36); p < 0.001; 18 ppb (5-89) vs 11 ppb (5-98); p < 0.05). Sensitivity and specificity of FENO for diagnosing atopic asthma (FENO≥15.5 ppb; AUC = 0.635, p < 0.01) were 61.1% and 64.9% and non-atopic asthma (FENO≥ 6.5 ppb; AUC = 0.445, p = 0.382) 54.1% and 39.2%, respectively. The PPV/NPV for FENO were 0.70/0.55 in atopy and 0.39/0.54 in non-atopy patients, respectively.
Conclusion:
In children, FENO is not appropriate to substitute for the MCT. However, in patients with a negative SPT a FENO in the normal range makes the presence of atopic asthma unlikely.