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

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.

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.

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.

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.