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

OBJECTIVES: To identify and synthesise evidence on the diagnostic accuracy of FE NO 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 FE NO50 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 FE NO 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: FE NO50 had variable diagnostic accuracy even within subgroups of studies with similar characteristics. Diagnostic accuracy, optimal cut-off values and best position for FE NO50 within a pathway remain poorly evidenced. This article is protected by copyright. All rights reserved.