Diagnosing asthma when laboratory breathing tests aren’t available
Published: July 20, 2021
International guidelines for diagnosing asthma stress the importance of lung function measurements such as spirometry, and where necessary bronchial challenge tests. These tests are not universally available, and, importantly, involve repeated forceful exhalation which can cause patients to cough and generate an aerosol of breath particles (procedures with aerosol generating potentials; AGPs). During the COVID-19 pandemic AGPs cannot be used in routine clinical practice due to the high risk of cross infection of COVID-19 via the spread of air droplets generated during the procedure. Therefore, another less risky way of diagnosing asthma is needed, which may also be of use in other situations where such specialized tests are not readily available.
This study reported in The Journal of Allergy and Clinical Immunology: In Practice, Drake & Wang et al describe the first results from the Rapid Access to Diagnostics in Asthma (RADicA - https://www.radica.org.uk/home.htm) research clinic, which has been set up in Manchester (UK) for general practitioners to refer patients with symptoms suggestive of asthma. At the clinic, participants are asked about their symptoms, examined and asked to perform all standard asthma diagnostic tests before and after treatment with regular inhaled corticosteroids. This includes procedures with in-clinic aerosol generating potential (spirometry-based tests including bronchodilator reversibility and bronchial challenge testing) and those without (non-AGPs, including audible wheeze on chest auscultation, fractional exhaled nitric oxide, blood eosinophils and home peak expiratory flow monitoring). At the end of the treatment period all these results are reviewed by a panel of asthma specialist physicians, who make a diagnostic decision in each case of “asthma” or “non-asthma”. Results from the expert panel were used to analyze the certainty with which a diagnosis of asthma could be made using AGPs’ compared to using non-AGPs only.
Sixty adults took part in the study. The research team found, in these patients with suspected asthma, that having one or more positive non-AGP test (i.e. wheeze on auscultation, high blood eosinophils and/or a variable home peak flow) confirms the diagnosis. Using such a diagnostic approach would reduce the need for spirometry-based tests by one-third. This strategy may be therefore be useful in situations where access to spirometry-based tests is limited.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.