Identifying opioid misuse in cancer pain: validation of the prescription opioid misuse index in a multicenter study.

Objectives: The prevalence of analgesic opioid (AO) misuse among patients with cancer-related chronic pain remains poorly understood, and no screening tool has been validated for this population. The Prescription Opioid Misuse Index (POMI), an eight-item self-administered questionnaire, was developed for chronic non-cancer pain. This study aimed to evaluate the psychometric properties of the POMI in a population of patients with chronic cancer-related pain.

Methods: This prospective observational psychometric study was conducted in two oncology day hospitals at the Clermont-Ferrand University Hospital. Eligible patients had active cancer, chronic pain lasting ≥ 3 months and were receiving daily opioid therapy. The POMI questionnaire was completed at inclusion (TEST) and 2 weeks later (RETEST). Psychometric properties were assessed following standard guidelines, including internal consistency, test-retest reliability and external validity using DSM-5 criteria for opioid use disorder as the reference standard.

Results: A total of 138 patients were included (58% men), with a mean age of 64 ± 10 years. Internal consistency of the POMI was low (Kuder-Richardson coefficient: 0.22). Test-retest reliability, assessed in 68 patients, showed moderate agreement (Lin's concordance: 0.43 [0.24-0.63]). Correlation between POMI scores and DSM-5 criteria was modest (Spearman's ρ = 0.25). According to the POMI, 11.6% of patients demonstrated opioid misuse versus 17.4% with DSM-5-defined use disorder.

Conclusions: The POMI lacks sufficient psychometric validity for use in oncology populations. Future tools should be specifically designed to address the clinical complexity and unique context of chronic cancer-related pain and opioid use.