Indigenous bronchiectasis assessment scale - the 'IBAS': a proposed new tool to assess bronchiectasis severity in adult Indigenous Australians.

Background: There is a lack of a comprehensive bronchiectasis severity assessment tool specific for Indigenous people that corrects for normative references established for the non-Indigenous population.

Objective: An innovative bronchiectasis assessment tool is developed for use in adult Indigenous patients - the Indigenous bronchiectasis assessment scale '(IBAS)'.

Methods: A total of 454 adult Indigenous Australian patients, with chest CT confirmed bronchiectasis diagnosed between 2011 and 2020, were included. Age, sex, residence location, body mass index, radiological findings, sputum microbiology, lung function parameters and medical comorbidities were utilised to predict 5-year all-cause mortality and 5-year hospitalisations. Scores of parameters with P < 0.20 from univariate Cox regressions were derived.

Results: The resultant IBAS included age (<30, 30-50, 50-70 and 70+ years), urban residence, forced vital capacity (% predicted) (>50%, 30%-50% and <30%), right lower lobe involvement, history of Haemophilus spp., Pseudomonas spp., yeast spp. or Moraxella spp., 2-year respiratory condition hospitalisation history (<2, 2 and 3+ admissions), and comorbid chronic obstructive pulmonary disease, asthma and arterial hypertension. The maximum score was 18, with thresholds at 0-4 (mild, n = 78, 34.4%), 5-7 (moderate, n = 111, 48.9%) and ≥ 8 (severe, n = 38, 16.7%). The area under the curve for 5-year mortality was 0.743 (95% confidence interval (CI) 0.683, 0.803). The IBAS score demonstrated significant delineation in mortality between mild and moderate (moderate hazard ratio (HR) 3.45 (95% CI 1.57, 7.58)) and between moderate and severe (severe HR 2.43 (95% CI 1.45, 4.07)).

Conclusions: The proposed IBAS tool could be of aid in assessing bronchiectasis severity in Indigenous patients.