Spirometry-Adjusted Fraction of Exhaled Nitric Oxide Allows Asthma Diagnosis in Children, Adolescents, and Young Adults

BACKGROUND: Recently, it has been proved that fractional exhaled nitric oxide (F ENO ) results are in disagreement with other measurements of asthma control. The objective of this work is to present and validate new lung function/lung inflammation ratios. METHODS: This is a retrospective, cross-sectional study in which we evaluated data from medical documentation of 1,529 pediatric and adolescent subjects and a small number (2% of the studied population) of young adults, who presented symptoms suggestive of asthma (age range 4–24 y). We are the first to analyze results obtained in this manner (before the introduction of controlled medication): F ENO , spirometry, specific resistance of the airways, diagnosis of allergic diseases, and allergen sensitization (specific immunoglobulin E results). RESULTS: Cut-off points for the new indicators allowed us to diagnose asthma in the study participants: for FVC/F ENO ratio, 0.17 L/ppb; for FEV 1 /F ENO ratio, 0.15 L/ppb; for forced expiratory flow during the middle half of the FVC maneuver (FEF 25–75% )/F ENO ratio, 0.16 L/s/ppb; for F ENO /FVC ratio, 11.00 ppb/L; for F ENO /FEV 1 ratio, 12.53 ppb/L; and for F ENO /FEF 25–75% ratio, 11.81 ppb/L/s. Only the ratios described above were closely correlated with the diagnosis of asthma and with one another. They significantly differed between subjects with asthma and healthy subjects as well as between females and males. Only FEF 25–75% /F ENO and F ENO /FEF 25–75% values were significant predictors of any sensitization in the studied subjects. We found higher sensitivity than specificity and higher positive predictive value than negative predictive value for FVC/F ENO , FEV 1 /F ENO , and FEF 25–75% /F ENO and found a mirror image for reverse parameters. However, the positive predictive values and negative predictive values were not clearly convincing with respect to diagnostic accuracy in the case of the new parameters proposed. CONCLUSIONS: We propose new lung function/lung inflammation ratios by which it may become possible to diagnose asthma in children and adolescents on the basis of a subject's spirometry and F ENO measurements. We believe that our ratios are only supportive of the universally used parameters in the process of diagnosing asthma. (ClinicalTrials.gov registration NCT01805635.)