Applicability and Validity of the "Bronchiectasis Severity Index" (BSI) and "FACED" Score in Adult Aboriginal Australians.

Background: The prevalence of bronchiectasis is significantly higher among adult Aboriginal Australians (the Indigenous peoples of Australia) compared to non-Aboriginal Australians. Currently, there is no well-established tool to assess bronchiectasis severity specific to Indigenous peoples. Nor has the applicability and validity of the two well-established bronchiectasis severity assessment tools - The "Bronchiectasis Severity Index" (BSI) and "FACED" scale been vigorously tested in an Indigenous population. This retrospective study evaluated the validity of the BSI and FACED amongst an adult Aboriginal Australian cohort with bronchiectasis in the Top End Northern Territory (NT) of Australia. Methods: Patients with CT confirmed bronchiectasis identified between 2011 and 2020, residing in the Top End of the NT were eligible to be enrolled. The primary endpoint of 4-year mortality was assessed via hospital records, and sensitivity and specificity of the BSI and FACED assessed against this using area under the curve (AUC) receiver operating characteristics analysis. For patients with missing data, a relative BSI / FACED score was used which divided the score recorded for that patient by the total potential score based on their available clinical data. Results: A total of 456 adult Aboriginal Australian patients >18 years of age were included (55.5% female, median age 49 years). According to the BSI score 43.4% of patients were assessed to have mild, 30.5% moderate and 26.1% severe bronchiectasis (median score 4 (IQR 2, 8)). According to the FACED 80.9% were assessed to have mild, 17.8% moderate and 1.3% severe (median score of 1 (IQR 0, 2)). Four-year mortality was 11.2% (median age of death 55.6 years). Sensitivity and specificity of the BSI combining moderate and severe were 86.3 and 47.2% respectively, and for severe alone 51% and 77%. Sensitivity and specificity of the FACED combining moderate and severe were 21.6% and 81.2%, respectively, and for severe alone 2% and 98.8%. The AUC for the continuous total BSI was 0.703, and the FACED 0.515. Utilising a relative score, based only on data available for patients with missing data (ie lung function or BMI) resulted in slightly improved AUCs for both the BSI (0.717) and FACED (0.571). Conclusion: Both BSI and FACED bronchiectasis assessment tools may not be ideal in an Indigenous/Aboriginal people's context. However, it may be reasonable to utilise the relative BSI score in this population until Indigenous people's specific bronchiectasis severity assessment tools are developed.