Asthma is a common long-term condition that can be difficult to diagnose accurately. Symptoms such as breathlessness, wheeze and cough can vary over time and may be caused by other conditions. Some people with asthma have normal breathing test results when they are assessed, which can make diagnosis challenging and lead to delays in treatment. This study aims to determine which commonly used tests, either alone or in combination, are most accurate for diagnosing asthma in adults with suspected disease. Participants referred to George Eliot Hospital for investigation of possible asthma will be invited to take part. Following informed consent, participants will undergo a range of routine diagnostic tests during their first visit. These include spirometry with bronchodilator response testing in patient with both normal airway function and airflow obstruction, fractional exhaled nitric oxide (FeNO), which measures airway inflammation, and oscillometry, which assesses how air moves through the lungs. Participants will then attend a second visit for a bronchial provocation challange test, which helps determine whether the airways are unusually sensitive, a key feature of asthma. The study will compare the results of these tests with the final diagnosis to assess how accurately each test identifies or excludes asthma. It will also investigate whether combining different tests improves diagnostic accuracy and whether factors such as obesity affect diagnostic measurements of increased asthma prevalence. The findings will help improve understanding of the most effective ways to diagnose asthma in routine clinical practice. This may lead to faster and more accurate diagnoses, reduce the need for unnecessary investigations, and support better care for people with suspected asthma.
Study Type
OBSERVATIONAL
Enrollment
2,176
Participants will undergo standardised pre-bronchodilator spirometry using a calibrated spirometer operated by trained study personnel. Measurements will include forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), slow vital capacity (SVC), peak expiratory flow (PEF) and the FEV₁/FVC ratio. Participants will perform at least three acceptable forced expiratory manoeuvres, with the highest reproducible values recorded. Spirometry will be conducted at the protocol-specified study visit(s) to assess pulmonary function as an outcome measure. Testing will follow current international quality control and acceptability standards.
Participants will undergo FeNO measurement using a calibrated nitric oxide analyser operated by trained study personnel. The test will be performed according to standardised international guidelines using a controlled exhalation at a constant flow rate. FeNO values, expressed in parts per billion (ppb), will be recorded to assess airway inflammation. Measurements will be obtained at protocol-specified study visit(s) under standardised testing conditions, with quality control procedures followed throughout testing.
Participants will undergo bronchodilator response testing to assess for airway responsiveness in both obstructive and normal patients. Spirometry will be performed before and after administration of a standardised dose of an inhaled short-acting bronchodilator delivered via a metered-dose inhaler with a spacer. Post-bronchodilator spirometry will be conducted after the protocol-specified waiting period. Changes in forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), and other spirometric parameters will be recorded according to standardised international guidelines. Testing will be performed by trained study personnel using calibrated equipment.
Participants will undergo respiratory oscillometry using a calibrated oscillometry device operated by trained study personnel. Measurements will be obtained during quiet tidal breathing according to standardised international guidelines. Respiratory impedance parameters, including airway resistance (e.g., R5, R20), reactance (e.g., X5), resonant frequency (Fres), and area of reactance (AX), will be recorded. At least three acceptable measurements meeting quality control criteria will be obtained. Testing will be performed at protocol-specified study visit(s) under standardised conditions to assess respiratory mechanics.
Participants will undergo a standardised bronchial provocation challenge to assess airway hyperresponsiveness. Increasing doses of a bronchial provoking agent will be administered according to a standardised protocol under the supervision of trained study personnel. Spirometry will be performed after each dose to measure changes in forced expiratory volume in one second (FEV₁). The test will continue until a predefined decline in FEV₁ is achieved or the maximum protocol dose is reached. Testing will be performed using calibrated equipment with continuous monitoring and appropriate safety procedures, following current international guidelines.
Physiological Sciences
Nuneaton, North Warwickshire, United Kingdom
Primary outcome measure- Sensitivity, Specificity, Positive Predictive Value, Negative Predictive Value, and Area Under the ROC Curve of Combined First-Line Objective Testing for Asthma Diagnosis
Diagnostic performance of combined first-line objective investigations (fractional exhaled nitric oxide \[FeNO\], oscillometry, spirometry, and bronchodilator reversibility testing) compared with the composite reference standard incorporating bronchial provocation testing. Diagnostic performance will be assessed using sensitivity, specificity, positive predictive value, negative predictive value, and area under the receiver operating characteristic curve (AUC).
Time frame: 6 weeks
Secondary out come measure - Number and Proportion of Participants Requiring Bronchial Provocation Testing Following First-Line Assessment
Number and proportion of participants who require bronchial provocation testing to confirm or exclude a diagnosis of asthma following completion of the first-line objective investigations.
Time frame: 6 weeks
Diagnostic Concordance Between First-Line Objective Investigations and the Composite Reference Standard
Diagnostic concordance between FeNO, oscillometry, spirometry, and bronchodilator reversibility testing and the composite reference standard incorporating bronchial provocation testing for the diagnosis of asthma.
Time frame: 6 weeks
Diagnostic Performance of First-Line Objective Investigations According to Obesity Status
Diagnostic performance of FeNO, oscillometry, spirometry, and bronchodilator reversibility testing compared with the composite reference standard, stratified according to obesity status using BMI, using the following categories: \<18.5 18.5-24.9 25-29.9 30-34.9 35-39.9 \>40
Time frame: 6 weeks
Diagnostic Performance of First-Line Objective Investigations in Participants With Preserved Baseline Spirometry
Diagnostic performance of FeNO, oscillometry, and bronchodilator reversibility testing compared with the composite reference standard among participants with preserved baseline spirometry.
Time frame: 6 weeks
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