FeNO testing for asthma diagnosis in primary care

Asthma is commonly misdiagnosed because there is no agreed gold standard. The National Institute of Clinical Excellence UK (NICE) recommends including the measurement of fractional exhaled nitric oxide (FeNO) in the diagnostic algorithm for asthma in adults. Diagnosing asthma occurs predominantly in primary care where investment and training in FeNO is limited and asthma is usually diagnosed based on history, spirometry, and treatment trial. Objective: To systematically evaluate patients with a primary care diagnosis of asthma to confirm/exclude asthma Method: 196 patients with a primary care diagnosis of asthma and on ICS treatment who had ongoing poor control (≥ 1 course of steroids, ≥ 6 SABA in the last 12 months (L12M), one healthcare utilisation episode in L12M and not known to secondary care) were evaluated in a rapid assessment clinic by an asthma multidisciplinary team (MDT) (doctor, nurse, physiotherapist and physiologist). This included spirometry, impulse oscillometry and FeNO measurement. Results: Asthma was confirmed in 169/196 patients (86%). 34 (20%) had FeNO ≥40ppb and 18 (11%) had obstructive spirometry; - 57 patients confirmed to have asthma were also found to have a breathing pattern disorder (BPD). Diagnosis of asthma was removed from 27 patients, of these, only 1 had FeNO ≥40ppb; -8 patients were diagnosed with COPD (1/8 had FeNO≥40ppb) -18 patients were diagnosed with a BPD Conclusion: Asthma was accurately diagnosed in 86% of patients, without the use of FeNO. Through a systematic MDT evaluation the diagnosis of asthma was removed from 14% of patients, almost all these patients had a low FeNO. FeNO measurement is a simple, non-invasive, optional test to support diagnostic uncertainty in primary care