Abstract

Background: Asthma diagnostic guidelines emphasise the importance of objective testing. With limited access to objective testing, many clinicians utilise clinical response to treatment for diagnosis. Asthma is characterised by temporal variability and symptoms may improve without treatment. We assess temporal variability in symptoms, lung function and airway inflammation at the diagnostic setting.


Methods: Participants aged 3-69 yrs with asthma symptoms and no recent inhaled corticosteroids were referred from primary care to the Rapid Access Diagnostics in Asthma (RADIcA) study. All participants completed baseline assessments at two time-points (visit 1, V1 and visit 2, V2) without change in treatment and 2-6 weeks apart, including: Asthma Control Questionnaire (ACQ), FeNO and spirometry (forced exhaled volume in 1 sec (FEV1)). Between-visit variability was assessed by determining the proportion of participants demonstrating the minimal clinically important difference (MCID) between visits.

Results: Of 645 symptomatic participants completing both visits, 429 were diagnosed with asthma (62% of adults, 73% of children; table). 1. Spontaneous improvement between visits: For adults there was a between-visit improvement >MCID for FeNO (20%), FEV1 (200mls) and ACQ (0.5) in asthma 29%, 24% and 35% respectively, and in non-asthma in 26%, 17% and 36%. For children with asthma there was an improvement in 36%, 12% and 45% respectively, and without asthma in 38%, 9%, and 39%. 2. Additional diagnoses from repeating FeNO: V1 FeNO was above the diagnostic threshold in 45% asthmatic adults (>50ppb) and 45% asthmatic children (>35ppb). FeNO was highly variable between visits (figure). Repeat FeNO testing at V2 identified an additional 21 (6%) asthmatic adults and 14 (8%) asthmatic children.

Conclusions: 1. Spontaneous improvement in inflammation, symptoms and lung function occurs commonly in people presenting with symptoms of asthma, regardless of their ultimate diagnosis. An assessment of “response to treatment” is therefore not helpful in making an asthma diagnosis. 2. Where spirometry is not readily available then repeating FeNO without treatment change can increase the number of patients diagnosed with asthma and therefore reduce the number requiring referral.