The usefulness of FeNO and the mannitol test in detecting airway eosinophilia in asthma patients with uncontrolled symptoms

2014 
Background :International guidelines recommend that anti-inflammatory treatment is up-titrated in asthma patients with poor symptom control. However in some patients, uncontrolled symptoms do not reflect airway inflammation, and these must be differentiated from patients with underlying eosinophilic inflammation. Exhaled nitric oxide (FeNO) and airway hyperresponsiveness (AHR) to mannitol both relate to eosinophilic airway inflammation. Aim: To determine the value of the mannitol test and FeNO to detect airway eosinophilia in asthma patients with uncontrolled symptoms. Methods: All patients referred consecutively over a 12-months period for specialist assessment of asthma at the Respiratory Outpatient Clinic at Bispebjerg Hospital in Copenhagen were examined with bronchial provocation, reversibility, FeNO and induced sputum. Results: Among 185 patients assessed, 133 (70%) had a diagnosis of asthma confirmed by at least one positive test (methacholine, mannitol or reversibility), 41% of whom had uncontrolled asthma symptoms with an ACQ score > 1.5. In patients with uncontrolled asthma symptoms and sputum eosinophils > 3%, the mannitol test was positive in 81%, and FeNO was > 25 ppb in 67% of subjects. Whereas sputum eosinophils were Conclusion: The mannitol test and FeNO were usefull for detecting presence or absence of airway eosinophilia, and may aid in the assessment of asthma patients with uncontrolled symptoms.
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