Prevalence of chronic pain in opioid-maintained patients using the capture-recapture method: a nationwide population-based study.

Few studies all based on classical surveys have provided prevalence estimates of chronic pain (CP) in opioid-maintained patients (OMPs) but often had a limited patient sample size and a great variability in the prevalence estimates. This study sought to assess the prevalence of CP in the exhaustive population of OMPs using the capture-recapture method applied to the French nationwide healthcare database. Capture-recapture methods are increasingly used to estimate the prevalence of chronic conditions but have never been used in the specific context of CP in OMPs. Three large medical-administrative sources were used: the prescription drug database (A-list), the national hospital discharge database (M-list), and the pain center database (C-list). Between 2015-2016, 160,429 OMPs ≥15 years old were identified and age- and sex-matched with 160,429 non-OMPs. All patients treated with analgesic drugs for ≥6months (A-list) or diagnosed with CP (M and C-list) were included. Capture-recapture analyses were performed to yield CP estimates with their 95% confidence intervals [95% CI] using log-linear models. In 2015-2016, 12,765 OMPs and 2,938 non-OMPs with CP were captured. Most patients were male (67%) in OMPs and non-OMPs; median ages for OMPs and non-OMPs were 46 (interquartile range: 38-51) and 48 (41-53) years, respectively. The CP prevalence estimated in OMPs and non-OMPs ranged from 23.6% [14.9-46.2] to 32.1% [28.6-36.3] and from 7.28% [3.98-18.4] to 9.32% [7.42-12.1], respectively. This first study on CP in the exhaustive population of OMPs using the capture-recapture method demonstrated a high prevalence of CP in OMPs, three to four-fold than in the general population.