Substance Use and Sex Index (SUSI): First stage development of an assessment tool to measure behaviour change in sexualised drug use for substance use treatment studies

The results support the conceptual basis for the instrument, highlighting the need for further scale content refinement to validate the tool and examine sensitivity to change. SUSI is a step towards improving outcome measurement of HIV/BBV/STI transmission risk behaviours in substance use treatment studies with greater inclusiveness of experiences across different population groups.