Background: Early identification of problems is essential in minimising the unintended consequences of opioid therapy. This study aimed to develop a brief scale that identifies and quantifies recent aberrant behaviour among diverse patient populations receiving long-term opioid treatment.

Method: 40 scale items were generated via literature review and expert panel (N  19) and tested in surveys of: (i) N = 41 key experts, and (ii) N  426 patients prescribed opioids >3 months (222 pain patients and 204 opioid substitution therapy (OST) patients). We employed item and scale psychometrics (exploratory factor analyses, confirmatory factor analyses and item-response theory statistics) to refine items to a brief scale.

Results: Following removal of problematic items (poor retest-reliability or wording, semantic redundancy, differential item functioning, collinearity or rarity) iterative factor analytic procedures identified a 10-item unifactorial scale with good model fit in the total sample (N = 426; CFI = 0.981, TLI = 0.975, RMSEA = 0.057), and among pain (CFI = 0.969, TLI = 0.960, RMSEA = 0.062) and OST subgroups (CFI = 0.989, TFI = 0.986, RMSEA = 0.051). The 10 items provided good discrimination between groups, demonstrated acceptable test–retest reliability (ICC 0.80, 95% CI 0.60–0.89; Cronbach's alpha = 0.89), were moderately correlated with related constructs, including opioid dependence (SDS), depression and stress (DASS subscales) and Social Relationships and Environment domains of the WHO-QoL, and had strong face validity among advising clinicians.

Conclusions: The Opioid-Related Behaviours In Treatment (ORBIT) scale is brief, reliable and validated for use in diverse patient groups receiving opioids. The ORBIT has potential applications as a checklist to prompt clinical discussions and as a tool to quantify aberrant behaviour and assess change over time.