Developing a patient reported measure on out-of-pocket healthcare expenditure among Aboriginal patients: a formative study.

Healthcare costs not subsidized by the government and are covered by patients, are known as out-of-pocket healthcare expenditure (OOPHE). In Australia, OOPHE disproportionately impacts Aboriginal households, particularly in rural and remote regions. Currently no patient reported measures (PRM) to assess OOPHE exist, despite being an identified priority in Aboriginal communities. This study developed and psychometrically evaluated (validity and test-retest reliability) of an OOPHE PRM for Aboriginal households in outer regional to remote areas. This Aboriginal led study was governed by an Aboriginal Governance Group, which involved a 4-stage process: (i) identification of community-derived OOPHE themes; (ii) item development and expert judgment quantification; (iii) exploratory factor analysis (EFA) to determine factor structure through pilot testing with Aboriginal participants; and (iv) assessment of reliability and stability through test-retest methods. Stage 1 identified OOPHE themes (i.e. barriers, financial strain), informing development of a 15 item PRM in Stage 2. In Stage 3, 39 Aboriginal participants completed Test 1, with EFA revealing a two-factor model; Factor 1 (8 items, internal consistency = 0.91) and Factor 2 (6 items, internal consistency = 0.85). In Stage 4, 32 participants completed Test 2, with over 60% of items showing substantial to perfect agreement (κ = 0.61-0.87) and scale-level reliability as good to excellent (ICC = 0.75-0.92). Two items performed poorly and were removed, resulting in a final 13-item PRM. The OOPHE PRM demonstrates promising psychometric properties as a culturally grounded measure of OOPHE burden among Aboriginal families, supporting advocacy for equitable policy, funding, and health system reform.