Physiological tests of small airways function in diagnosing asthma: a systematic review

Mohammed Almeshari, Nowaf Alobaidi, Ross Edgar, James Stockley, Elizabeth Sapey

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Background: Asthma is a common, heterogeneous disease that is characterized by chronic airway inflammation and variable expiratory airflow limitation. Current guidelines use spirometric measures for asthma assessment. This systematic review aimed to assess whether the most commonly reported tests of small airways function could contribute to the diagnosis of asthma.

Methods: Standard systematic review methodology was used, and a range of electronic databases was searched (Embase, MEDLINE, CINAHL, CENTRAL, Web of Science, DARE). Studies that included physiological tests of small airways function to diagnose asthma in adults were included, with no restrictions on language or date. The risk of bias and quality assessment tools used were AHRQ tool for cross-sectional studies and QUADAS-2 for diagnostic test accuracy (DTA) studies.

Results: 7072 studies were identified, and 10 studies met review criteria. 7 included oscillation techniques and 5 included maximal mid-expiratory flow (MMEF). Studies were small and of variable quality. In oscillometry, total resistance (R5) and reactance at 5 Hz (X5) was altered in asthma compared to healthy controls. The percentage predicted of MMEF was lower in patients with asthma compared to controls in all studies and lower than the % predicted FEV1. In DTA of oscillometry, R5 showed a sensitivity between 69-72% and specificity between 61- 86%.

Conclusion: There were differences in the results of physiological tests of small airway function in patients with asthma compared to controls. However, studies are small and heterogeneous. Further studies are needed to assess the effectiveness of these tests on a larger scale, including studies to determine which test methodology is the most useful in asthma
Original languageEnglish
Article numbere000770
JournalBMJ Open Respiratory Research
Issue number1
Publication statusPublished - 21 Dec 2020


  • Asthma
  • Diagnosis
  • Small Airways
  • physiology
  • spirometry
  • Oscillometry
  • MMEF
  • FEV1


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