Can we diagnose asthma using standard nonaerosol generating procedures?

ABSTRACT

Objective: Asthma diagnostic guidelines from NICE mandate up to five tests in a sequential algorithm, three of which are aerosol generating procedures (AGPs) [spirometry, reversibility (BDR), bronchial challenge testing (BCT)]. The SARS-CoV-2 pandemic has resulted in significant restrictions to AGPs, highlighting the urgent need for an alternative diagnostic model. We aimed to develop a 'rule-in' diagnostic model using non AGPs [chest auscultation, exhaled nitric oxide (FeNO), two week-peak flow variability (PEFv) and serum eosinophils (eos)] which would enable GPs to confidently diagnose asthma in a subgroup of patients and reduce the need for AGPs and onward referral. Methods: Symptomatic but untreated patients with physician-suspected asthma were referred into the RADicA (Rapid Access Diagnostics in Asthma) study. Patients underwent clinical consultation followed by tests including FeNO, spirometry, BDR, PEFv, BCT, and eos. Asthma diagnosis was made on the basis of all available information (including response to eight weeks inhaled corticosteroid treatment) by a panel of respiratory physicians. Data from patients coded as 'definite asthma' or 'not asthma' were evaluated, individually and in combination in order to investigate which non-AGP tests could predict asthma. PEFv was classified as a non-AGP because it is not performed in the clinical setting. Results: Of 61 symptomatic adults [median (IQR) age 32(26-44)yrs, 62% female] 61% had 'definite asthma' by expert panel decision. Each of the four non-AGP tests were able to predict asthma with low sensitivity and high specificity (figure 1). Using established cut-offs (PEFv>20%, FeNO≥40ppb, eos>0.4 × 109/L), an algorithm which simply required the presence of two or more positive tests was able to 'rule-in' asthma with a specificity (95% CI) of 100(78-100)%, sensitivity 20(8-39)%. In comparison using all available tests required for the NICE algorithm resulted in a sensitivity of 53(34-72)%, specificity 100(79-100)%. Conclusion: Four simple non-AGPs could be used in primary care to accurately diagnose asthma. The majority of patients (Figure presented) with negative tests would still require further investigation, and so it is clear that AGPs, or novel alternatives, are still required for the diagnosis of asthma in most patients.