The Prevalence of Bronchodilator Responsiveness “Asthma” Among Adult Indigenous Australians Referred for Lung Function Testing in the Top End Northern Territory of Australia

Abstract

Subash S Heraganahally,1– 3 Timothy P Howarth,3,4 Angus Lloyd,1 Elisha White,3 Antony Veale,5 Helmi Ben Saad6 1Department of Respiratory and Sleep Medicine, Royal Darwin Hospital, Darwin, Northern Territory, Australia; 2College of Medicine and Public Health, Flinders University, Adelaide, South Australia, Australia; 3Darwin Respiratory and Sleep Health, Darwin Private Hospital, Darwin, Northern Territory, Australia; 4College of Health and Human Sciences, Charles Darwin University, Darwin, Northern Territory, Australia; 5Department of Respiratory and Sleep Medicine, Queen Elizabeth Hospital, Adelaide, South Australia, Australia; 6Faculty of Medicine of Sousse, Hospital Farhat HACHED of Sousse, Research Laboratory “Heart Failure, LR12SP09”, University of Sousse, Sousse, TunisiaCorrespondence: Subash S Heraganahally, Department of Respiratory and Sleep Medicine, Royal Darwin Hospital, Darwin Respiratory and Sleep Health, Darwin private Hospital, Darwin, Northern Territory, Australia, Tel [phone], Fax [phone], Email [email protected]; [email protected]: Among Indigenous Australians, studies examining the clinical significance of airway bronchodilator responsiveness (BDR) are limited. In this retrospective study, we examined the nature of underlying lung disease in adult Indigenous patients with BDR referred for lung function testing (LFT) in the Top End Health Service region of the Northern Territory of Australia.Methods: Presence or absence of BDR as per usual (FVC or FEV1 change pre to post ≥ 12% and ≥ 0.2L) and updated (2021 “> 10% predicted) ATS/ERS criteria among Indigenous and non-Indigenous Australians was determined. The radiological findings in the Indigenous study participants with and without BDR were next assessed for the presence of underlying chronic airway/lung disease.Results: We found that 123/742 (17%) Indigenous and 578/4579 (13%) non-Indigenous patients had a significant BDR. Indigenous patients with BDR were younger (mean difference 7 years), with a greater proportion of females (52 vs 32%), underweight (15 vs 4%) and current smokers (52 vs 25%). Indigenous patients with BDR displayed lower LFT values, and a higher proportion exhibited FVC BDR compared to non-Indigenous (34 vs 20%). Almost half (46%) of Indigenous patients with BDR had evidence of COPD and/or bronchiectasis on radiology. Adjusting for the presence of radiologic or spirometric evidence of COPD, the presence of BDR was similar between Indigenous and non-Indigenous patients (5– 8 vs 7– 11%), irrespective of which BDR criteria was used.Conclusion: BDR was higher overall among Indigenous in comparison to non-Indigenous patients; however, a significant proportion of Indigenous patients demonstrating BDR had evidence of underlying COPD/bronchiectasis. This study highlights that although presence of BDR among Indigenous people may indicate asthma, it may also be observed among patients with COPD/bronchiectasis or could represent asthma/COPD/bronchiectasis overlap. Hence, a combination of clinical history, LFT and radiology should be considered for precise diagnosis of lung disease in this population.Keywords: asthma, airway obstruction, first nations, radiology imaging, reversible airflow obstruction, spirometry

Keywords

• asthma
• airway obstruction
• first nations
• radiology imaging
• reversable airflow obstruction
• spirometry