Exhaled nitric oxide in the diagnosis of asthma in adults: a systematic review

Objectives To identify and synthesise evidence on the diagnostic accuracy of FENO for asthma in adults. Materials And Methods Systematic searches (nine key biomedical databases and trial registers) were carried out to November 2014. Records were included if they: recruited patients with the symptoms of asthma; used a single set of inclusion criteria; measured FENO50 in accordance with American Thoracic Society guidelines, 2005 (off-line excluded); reported/allowed calculation of true positive, true negative, false positive and false negative patients as classified against any reference standard. Study quality was assessed using QUADAS II. Meta-analysis was planned where clinical study heterogeneity allowed. Rule-in and Rule-out uses of FENO were considered. Results 4861 records were identified originally and 1312 in an update. 27 studies were included. Heterogeneity precluded meta-analysis. Results varied even within subgroups of studies. Cut-off values for the best sum of sensitivity and specificity varied from 12ppb to 55ppb, but did not produce high accuracy. 100% sensitivity or 100% specificity were reported by some studies indicating potential use as a rule-in or rule-out strategy. Conclusions FENO50 had variable diagnostic accuracy even within subgroups of studies with similar characteristics. Diagnostic accuracy, optimal cut-off values and best position for FENO50 within a pathway remain poorly evidenced. This article is protected by copyright. All rights reserved.