Background:
It is well established that racism is a fundamental contributor to poor health and inequities. There is consistent evidence of high exposure to discrimination among Aboriginal and Torres Strait Islander (Indigenous Australian) peoples, but impacts have not been fully quantified, in part due to limited measurement tools. This research aims to validate instruments developed to measure interpersonal discrimination.

Methods:
Instruments were discussed at five focus groups and with experts, and field tested in developing Mayi Kuwayu: The National Study of Aboriginal and Torres Strait Islander Wellbeing. Data from 7501 baseline survey participants were analysed. Acceptability was assessed according to extent of missingness, construct validity using exploratory and confirmatory factor analysis, and reliability using Cronbach’s alpha. Associations between each instrument and outcomes conceptually understood to be closely (community-level racism) or less closely (family wellbeing) related were quantified to test convergent and discriminant validity.

Results:
An 8-item instrument captures experiences of discrimination in everyday life and a 4-item instrument experiences in healthcare, each followed by a global attribution item. Item missingness was 2.2–3.7%. Half of participants reported experiencing any everyday discrimination, with 65.7% attributing the discrimination to Indigeneity; healthcare discrimination figures were 34.1% and 51.1%. Items were consistent with two distinct instruments, differentiating respondents with varying experiences of discrimination. Scales demonstrated very good reliability and convergent and divergent validity.

Conclusion:
These brief instruments demonstrate face validity and robust psychometric properties in measuring Aboriginal and Torres Strait Islander adults’ experiences of interpersonal discrimination in everyday life and in healthcare. They can be used to quantify population-level experiences of discrimination, and associated wellbeing consequences, and monitor change.