: Developing economic measures for Aboriginal and Torres Strait Islander families on out-of-pocket healthcare expenditure.

Objective Out-of-pocket healthcare expenditure (OOPHE) has a significant impact on marginalised households. The purpose of this study was to modify a pre-existing OOPHE survey for Aboriginal and Torres Strait Islander households with children. Methods The OOPHE survey was derived through a scoping review, face and content validity, including judgement quantification with content experts. Exploratory factor analyses determined factor numbers for construct validity. Repeatability through test-retest processes and reliability was assessed through internal consistency. Results The OOPHE survey had 168 items and was piloted on 67 Aboriginal and Torres Strait Islander parents. Construct validity assessment generated a 62-item correlation matrix with a three-factor model. Across these factors, item loadings varied, 10 items with high correlations (>0.70) and 20 with low correlations (Conclusion The low level of item loadings to factors in the OOPHE survey indicates interconnectedness across the three-factor model, and reliability results suggest systemic differences. Impeding factors may include cohort homogeneity and survey length. It is unknown how cultural and social nuances specific to Aboriginal and Torres Strait Islander households impacts on results. Further work is warranted. What is known about the topic? Out-of-pocket healthcare expenditure (OOPHE) are expenses not covered by universal taxpayer-funded health insurance. In elderly Australians or those with chronic conditions, OOPHE can cause substantial burden and financial hardship and, in the most extreme cases, induce bankruptcy. Despite higher hospital admissions and disease burden, little is known about how OOPHE impacts Aboriginal and Torres Strait Islander families. Additionally, in Australia, no OOPHE survey tools have been appropriately assessed; this includes for use with Aboriginal and Torres Strait Islander families. What does this paper add? This pilot study modified a pre-existing Australian OOPHE survey for use with Aboriginal and Torres Strait Islander households with children. Knowledge interface methodology was used to bring together Indigenous knowledges with quantitative survey methods. This was critical to ensuring Indigenous knowledges were central to the overall pilot study across item creation, participant focus, outcome contextualisation, interpretation, and resetting dominant norms. Outcomes have demonstrated pertinent points for future work in this area, such as the complexities in developing robust, culturally safe and specific surveys, which reach ideal psychometric levels of validity and reliability for Aboriginal and Torres Strait Islander communities. Certainly, it raises questions for current and future research using surveys in Aboriginal and Torres Strait Islander communities, which are generic and not purpose-built. What are the implications for practitioners? We recommend that OOPHE surveys should be developed with Aboriginal and Torres Strait Islander families from the outset, so they can include important contextual factors for Aboriginal and Torres Strait Islander households.