OP3 ASTHMA AND SMALL AIRWAY DISEASE – A RELOOK AT DIAGNOSIS: SPIROMETRY VS IOS – PRELIMINARY DATA

Nuruliman Binti Dashuki, Aisya Natasya Musa, Wong Yen Shen, Mohd Zhafran Zainal Abidin, Affida Ahmad
Faculty of Medicine, Universiti Teknologi MARA (UiTM), Sungai Buloh, Selangor, Malaysia

Introduction:

Asthma diagnosis is challenging, mainly relying on clinical diagnosis supported by evidence of variable airflow limitation. Although spirometry is widely accepted as a tool to diagnose asthma, it is limited by the ability of patients to perform it unlike impulse oscillometry (IOS). IOS is also used to diagnosed small airway disease (SAD), yet, there are limited study comparing both diagnostic tools.

Methods:

This is a cross-sectional study conducted at the Respiratory Clinic, Hospital Al-Sultan Abdullah starting in December 2023. Patients with a known diagnosis of asthma and aged 18 years and above were included in this study. Exclusion criteria were asthma exacerbation within the last 4 weeks, pregnant, has other lung diseases and active respiratory infection. Participants underwent both spirometry and IOS test before and after bronchodilator (BD). Demographic data, Asthma Control Test (ACT) scores, and, spirometry and IOS parameters were collected and analysed.

Results:

110 patients were included in this study with a mean age of 49.98±16.05 year and mean BMI of 29.65±5.93 kg/m2. 80% were female and 87.3% were non-smokers. 75% had well-controlled asthma. Mean FEV1 pre-BD was 72.00±16.95% and mean FEV1/FVC ratio was 73.90±12.45%. FEV1 was <80% predicted in 68.2% of patients. Post-BD, 31.8% had FEV1 increment of 200mls and 30.9% had FEV1 change of 12%. 27.3% fulfilled GINA/ATS criteria compared to 26.4% fulfilled ERS criteria for reversibility. 47.3% fulfilled IOS reversibility criteria. SAD was identified in 80.7% of patients using spirometry as compared to 87.3% of patients using IOS. There was no significant association between presence of SAD (either on spirometry or IOS) and asthma control.

Conclusion:

ATS and IOS reversibility criteria appeared to be more sensitive in diagnosing asthma. IOS is also more sensitive in diagnosing small airway disease, however, there was no association seen with asthma control.