Explore the Diagnostic Value of Bronchodilation Test With Portable Oscillometry in Asthma Diagnosis

Following the completion of informed consent procedures, patients with asthmatic symptoms will proceed to enrollment for inclusion and exclusion criteria review. In addition, blood tests, include complete blood count (CBC) and C-reactive protein (CRP), and chest Computed Tomography (CT) will be done for eligible participants prior to all assessments in the study to ensure excluding participants with respiratory infections and any lung diseases (other than asthma).

All the included participants will undergo Fractional exhaled nitric oxide (FeNO) test, BDT with portable oscillometry and spirometry in sequence and complete the Asthma Control Questionnaire-5 (ACQ-5) assessment during Visit 1. For participants with pre-BD FEV1% ≥ 70% will undergo BPT with spirometry as the last assessment in the study.

The diagnosis of asthma will be defined as positive BDT (after bronchodilator inhalation, FEV1 increased by ≥12%, and the absolute value of FEV1 increased by ≥200 mL) or positive BPT with spirometry (FEV1% decrease ≥20% after methacholine inhalation). Oscillometry BDT positive is defined as R5 decrease 40%, or X5 increase 50%, or AX decrease 80% after bronchodilator inhalation as recommended in ERS consensus.

Inclusion criteria

Participants must meet all the following criteria and sign an informed consent form (ICF) to be eligible for the study.

• Patient must be aged 18-75 years old at the time of enrollment.
• Presented with asthmatic symptoms such as wheezing, shortness of breath, chest tightness and cough ≥2 months prior to enrollment (Day 0), with/without an established asthma diagnosis.

Exclusion criteria

Patients are excluded from the study if any of the following criteria apply:

Medical Conditions

• Respiratory infections within 3 months prior to enrollment (Day 0), including but not limited to: acute bacterial/viral pneumonia, acute bronchitis, Influenza, COVID-19 or acute exacerbation of chronic bronchitis.
• Current smoker; or cessation from smoking less than 6 months; or cessation smoking for more than 6 months but smoked more than 10 packs/year.
• History of other chronic respiratory diseases other than asthma, including but not limited to tuberculosis, significant bronchiectasis, established interstitial lung disease, and lung cancer.
• History of serious comorbidities, including, but not limited to, cardiovascular, gastrointestinal, hepatic, renal, neurological, musculoskeletal, infectious, endocrine, metabolic, haematological, psychiatric, or major physical impairment that is not stable in the opinion of the investigator and could:

• Affect the safety of the patient throughout the study,
• Confound the study results or impact the scientific validity of the data outcome,
• Impede the patient's ability to complete the entire duration of study.
• Positive urine pregnancy test, or breastfeeding women, or any women who are planning to become pregnant (current and within 3 months).

Prior/Concomitant Therapy

• ICS-based medication (including ICS, ICS/LABA, ICS/LABA/LAMA) use within 3 months prior to enrollment (Day 0).

ICS=inhaled corticosteroids; LABA=long-acting β2 agonists; LAMA=long-acting muscarinic antagonists.

Other Exclusions

• Judgment by the investigator that the participant should not participate in the study if the participant is unlikely to comply with study procedures, restrictions, and requirements.
• Current participation in another interventional clinical trial.