title: Diagnosing asthma: comparisons between exhaled nitric oxide measurements and conventional tests.
abstract: International guidelines recommend a range of clinical tests to confirm the diagnosis of asthma. These focus largely on identifying variable airflow obstruction and responses to bronchodilator or corticosteroid. More recently, exhaled nitric oxide (FE(NO)) measurements and induced sputum analysis to assess airway inflammation have been highlighted. However, to date, no systematic comparisons to confirm the diagnostic utility of each of these methods have been performed. To do so, we investigated 47 consecutive patients with symptoms suggestive of asthma, using a comprehensive fixed-sequence series of diagnostic tests. Sensitivities and specificities were obtained for peak flow measurements, spirometry, and changes in these parameters after a trial of steroid. Comparisons were made against FE(NO) and sputum cell counts. Sensitivities for each of the conventional tests (0-47%) were lower than for FE(NO) (88%) and sputum eosinophils (86%). Overall, the diagnostic accuracy when using FE(NO) and sputum eosinophils was significantly greater. Results for conventional tests were not improved, using a trial of steroid. We conclude that FE(NO) measurements and induced sputum analysis are superior to conventional approaches, with exhaled nitric oxide being most advantageous because the test is quick and easy to perform.
authors.affiliation: Dunedin School of Medicine, University of Otago Medical School, Dunedin, New Zealand.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Smith
authors.forename: Jan O
authors.initials: JO
authors.lastname: Cowan
authors.forename: Sue
authors.initials: S
authors.lastname: Filsell
authors.forename: Chris
authors.initials: C
authors.lastname: McLachlan
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Monti-Sheehan
authors.forename: Pamela
authors.initials: P
authors.lastname: Jackson
authors.forename: D Robin
authors.initials: DR
authors.lastname: Taylor
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001249:Asthma / Q000175:diagnosis*; D001944:Breath Tests; D002648:Child; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis*; D011237:Predictive Value of Tests; D012129:Respiratory Function Tests; D012680:Sensitivity and Specificity; D014797:Vital Capacity
chemical_list: D009569:Nitric Oxide