Fraction of exhaled nitric oxide in patients with acute eosinophilic pneumonia

Background: Acute eosinophilic pneumonia (AEP) is an idiopathic disease characterized by pulmonary eosinophilia. Because the fraction of exhaled nitric oxide (F ENO) is a surrogate of eosinophilic inflammation, we evaluated the levels, changed treatments, and the diagnostic role of F ENO in patients with AEP. Methods: Between June 2010 and March 2011, we prospectively enrolled patients at the Armed Forces Capital Hospital who had pulmonary infiltrates and a febrile illness and who were clinically suspected to have AEP. We measured F ENO twice at the initial visit (pretreatment) and 2 weeks after the initial measurement (posttreatment). Results: A total of 60 subjects were enrolled, and 31 were given a diagnosis of AEP. The pretreatment F ENO levels of the patients with AEP were significantly higher than those of the patients without AEP (median, 48 parts per billion [ppb] [range, 10-138] vs 14 ppb [range, 5-41]; P<.001). The cut-off value (23.5 ppb) showed that the maximal area under the receiver operating characteristic curve predicted AEP with a sensitivity of 0.87 and a specificity of 0.83. The posttreatment F ENO levels decreased significantly in the patients with AEP, and the levels were similar to the patients without AEP (median, 19 ppb [range, 7-44] vs 14 ppb [range, 1-58]; P =.21) Conclusions: The F ENO level was significantly higher in patients with AEP than in those without AEP. F ENO measurement can be used as a diagnostic tool to differentiate patients with AEP from those without AEP. Trial Registry: ClinicalTrials.gov; No.: NCT01152424; URL: www.clinicaltrials.gov.