Characterising airway inflammation in Aboriginal and Torres Strait Islander and non-Aboriginal and Torres Strait Islander adults with asthma and COPD

Abstract

To examine airway inflammatory cell profiles in Indigenous Australian adults with asthma and chronic obstructive pulmonary disease (COPD). A retrospective, cross-sectional study on data from a tertiary referral respiratory outpatient clinic. Indigenous (n=23) and non-Indigenous (n=71) adults were matched according to diagnosis, gender and age to the ratio of 1:3. Participants were defined by self-determined identification as Indigenous (Aboriginal) or non-Indigenous. A relevant history was taken, and lung function was measured by spirometry. In those with a diagnosis of asthma, symptom control was assessed by the Asthma Control Questionnaire, six items (ACQ6). In those with a diagnosis of COPD, symptoms were assessed by the COPD assessment test (CAT). Airway cell counts were obtained in all groups from bronchial lavage (BL) cell count. Lung function and inhaled corticosteroid dose were similar between groups. Current smoking was three times more common in Indigenous people (35%) compared with non-Indigenous people (12%, p=0.009). In participants with asthma, ACQ6 scores were similar between Indigenous and non-Indigenous participants with asthma. In those with COPD, Indigenous participants had significantly higher total CAT scores as well as scores for cough and sputum with a score indicating a high impact on quality of life (CAT score ≥14, 85%-25%, p=0.017). There was no difference in BL cell differential counts. Indigenous people with COPD had higher smoking rates, worsened CAT scores and more symptoms of cough and sputum production. There were no differences between the groups in airway inflammation, but neutrophilic inflammation was associated with poorly-controlled asthma.