P118 Measuring FeNO in the diagnosis of asthma does repeating the test improve diagnostic certainty in the RADicA study

Introduction and Objectives Fractional exhaled Nitric Oxide (FeNO) is an essential test for asthma diagnosis in the NICE algorithm (NG80). A characteristic feature of asthma is the variability of symptoms and signs. Within the setting of our Rapid Access Diagnostics for Asthma (RADicA) research clinic, we investigated whether repeat testing of FeNO in those with borderline or negative results improved diagnostic certainty. Methods Adults and children with symptoms of cough, wheeze, breathlessness or chest tightness were referred by primary care for a comprehensive assessment. FeNO (NIOX VERO, Circassia) was measured on two separate occasions a minimum of 5 days apart prior to starting inhaled corticosteroids. FeNO result was classified according to NG80 for adults (FeNO ≥ 40ppb positive, 25–39ppb borderline, Results 112 participants (66% adult, 56% female) achieved FeNO on at least one of these visits; 86 completed both measures. FeNO levels were similar between the two visits (V1 median 22ppb [IQR 54ppb], V2 median 23.5ppb [IQR 45ppb], p=0.52; r=0.91 p Conclusions Although there was a strong correlation between FeNO measured on 2 separate occasions prior to starting treatment, almost one in four of those with a borderline test went on to have a positive test when given the opportunity to repeat. Repeating FeNO in those with a borderline result would reduce the proportion of patients requiring referral to secondary care, at low cost.