Healthcare use by people who use illicit opioids (HUPIO): development of a cohort based on electronic primary care records in England

Abstract

Background: People who use illicit opioids such as heroin have substantial health needs, but there are few longitudinal studies of general health and healthcare in this population. Most research to date has focused on a narrow set of outcomes, including overdoses and HIV or hepatitis infections. We developed and validated a cohort using UK primary care electronic health records (Clinical Practice Research Datalink GOLD and AURUM databases) to facilitate research into healthcare use by people who use illicit opioid use (HUPIO). Methods: Participants are patients in England with primary care records indicating a history of illicit opioid use. We identified codes including prescriptions of opioid agonist therapies (methadone and buprenorphine) and clinical observations such as ‘heroin dependence’. We constructed a cohort of patients with at least one of these codes and aged 18-64 at cohort entry, with follow-up between January 1997 and March 2020. We validated the cohort by comparing patient characteristics and mortality rates to other cohorts of people who use illicit opioids, with different recruitment methods. Results: Up to March 2020, the HUPIO cohort included 138,761 patients with a history of illicit opioid use. Demographic characteristics and all-cause mortality were similar to existing cohorts: 69% were male; the median age at index for patients in CPRD AURUM (the database with more included participants) was 35.3 (IQR 29.1-42.6); the average age of new cohort entrants increased over time; 76% had records indicating current tobacco smoking; patients disproportionately lived in deprived neighbourhoods; and all-cause mortality risk was 5.4 (95% CI 5.3-5.5) times the general population of England. Conclusions: Primary care data offer new opportunities to study holistic health outcomes and healthcare of this population. The large sample enables investigation of rare outcomes, whilst the availability of linkage to external datasets allows investigation of hospital use, cancer treatment, and mortality.

Healthcare use by people who use illicit opioids (HUPIO): development of a cohort based on electronic primary care records in England

“…The distribution of age groups was similar to that of patients entering treatment for opioid dependence in England (see extended data 23 ). We observed a linear increase in the mean age of patients entering our cohort, parallel and three years older than the mean age of patients entering treatment for opioid dependence in England (see extended data 23 ). When stratified by date, the mean age of patients entering the cohort was similar for GOLD and AURUM.…”

“…First, we described the age-and sex-distribution of patients at the time of the first prescription. This showed two distinct groups: drugs mainly prescribed to younger men, and drugs mainly prescribed to older women (see extended data 23 ). Data from specialist drug treatment services shows that the population receiving OAT is three-quarters male and predominantly aged 18-64 28 .…”

“…Product codes indicate a prescription made in a primary care setting, whilst clinical codes indicate a diagnosis or other clinical observation (sometimes also a prescription). We selected patients by identifying product codes indicating a prescription of OAT and clinical codes indicating a history of illicit opioid use, such as 'heroin dependence' (see extended data for a full code list 23 ). We prioritised specificity over sensitivity, aiming to use codes that are only applied to the target population.…”

“…We searched CPRD dictionaries to identify all methadone and buprenorphine product codes (full search terms are available as extended data 23 ). We found 175 codes in CPRD GOLD and 136 codes in CPRD AURUM.…”

“…The method developed in this study avoids the need for imputation by using products that are specific to OAT. It is possible that we excluded some medicines that are used for OAT in addition to other indications, though few patients with prescriptions of excluded methadone or buprenorphine products had other codes indicating a history of illicit opioid use (see extended data 23 ).…”