Objective: To evaluate the diagnostic accuracy of fractional exhaled nitric oxide (FeNO) measurement in individuals with suspected asthma. Methods: We searched MEDLINE, EMBASE, PsycINFO, Cochrane databases, and SciVerse Scopus from the databases' inception through April 4, 2017, for studies that enrolled patients aged 5 years and older with suspected asthma and evaluated FeNO diagnostic accuracy. Independent reviewers selected studies and extracted data. We used the symmetric hierarchical summary receiver operating characteristic models to estimate test performance. Results: We included 43 studies with a total of 13,747 patients. In adults, using FeNO cutoffs of less than 20, 20 to 29, 30 to 39, and 40 or more parts per billion, FeNO testing had sensitivities of 0.80, 0.69, 0.53, and 0.41, respectively, and specificities of 0.64, 0.78, 0.85, and 0.93, respectively. In children, using FeNO cutoffs of less than 20 and 20 to 29 parts per billion, FeNO testing had sensitivities of 0.78 and 0.61, respectively, and specificities of 0.79 and 0.89, respectively. Depending on the FeNO cutoff, the posttest odds of having asthma with a positive FeNO test result increased by 2.80- to 7.00-fold. Diagnostic accuracy was modestly better in corticosteroid-naive asthmatics, children, and nonsmokers than in the overall population. Conclusion: Fractional exhaled nitric oxide measurement has moderate accuracy to diagnose asthma in individuals aged 5 years and older. Test performance may be modestly better in corticosteroid-naive asthmatics, children, and nonsmokers than in the general population with suspected asthma. Trial Registration: International Prospective Register of Systematic Reviews (PROSPERO) Identifier: CRD42016047887.
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