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Provincial Overdose Cohort

The BC Provincial Overdose Cohort consists of de-identified data on persons who have experienced an illicit drug overdose in British Columbia.

Overview

The Provincial Overdose Cohort is a collection of linked administrative data on overdose events that is combined with data about prescription drugs, healthcare use, and incarceration in a provincial correctional institution. Data on overdose events is from January, 1 2015 to December 31, 2018, and includes appended health history data from the preceding five years. The structure of the data provides a method to measure longitudinal health histories before, during, and after an overdose. 

The analytic outputs generated from the Provincial Overdose Cohort help the province to better understand factors that lead to non-fatal overdose and overdose death. This information helps targeted programmatic responses to the overdose crisis. Furthermore, the cohort’s products help identify patterns of healthcare use in order to identify opportunities for intervention and appropriate targeting of public health messaging. 

The Cohort can also be used to evaluate the impact of interventions in response to the public health emergency, and evaluate long-term health outcomes of people who have overdosed. The Cohort is refreshed annually and will be available for use by all partner organizations involved in the overdose response (e.g. Health Authorities).

Data sources

The Provincial Overdose Cohort is composed of linked administrative data on health care utilization by people experiencing an opioid drug overdose in B.C. 

Persons who have had an illicit drug overdose were identified using data from:

  • B.C. Ambulance Service (BCAS)
  • Drug and Poison Information Centre (DPIC)
  • BC Coroners Service (BCCS)
  • Case-based reporting from Emergency Departments
  • National Ambulatory Care Reporting System (NACRS)
  • Discharge Abstract Database (DAD)
  • Medical Services Plan (MSP)

Five years of health history is appended at a patient level from:

  • DAD (all hospital discharge summaries)
  • NACRS (all emergency department visits)
  • MSP (all fee-for-service physician billing records)
  • PharmaNet (all prescription dispensations in community pharmacies)
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Additional data, such as records from BC Corrections, are appended to the Provincial Overdose Cohort.  

Cases

The cohort includes persons who have had an overdose since January 1, 2015. This period represents the beginning of the rapid rise in illicit drug overdoses and deaths in B.C. 

An overdose event is defined by any of the following criteria: 

  • administration of the opioid antagonist naloxone by paramedics
  • a call to DPIC about an opioid-related event
  • physician-diagnosed opioid overdose at the emergency department (from case-based reporting)
  • coroner-determined illegal drug overdose death
  • visit to hospital, emergency department or physician with an associated opioid overdose diagnosis code (from DAD, NACRS or MSP)

Related events present in multiple datasets (e.g., a single overdose involving ambulance response, transport to emergency department and admission to hospital) are grouped to prevent over counting of overdoses.

Controls

A reference population is available for analysis. The reference group is selected from a 20% random sample of the B.C. population with overdose cases removed. A matched control population is also available. Previous cohort analyses featured 1:5 matching without replacement based on birth year, sex and Local Health Area of residence. Similar to cases, health and prescribing histories are available for this group. 

Exclusions

Some persons who experienced an overdose but were unable to be linked to administrative data sources through personal health numbers were not included in the cohort (12% of all overdose cases). Furthermore, persons whose overdose events were not captured through administrative data sources (i.e. those who did not access healthcare services for their overdose) will be excluded.

Potential uses

Here are some examples of potential uses of the Provincial Overdose Cohort:

  • Analyses that require linkage: The Cohort is well suited to answer questions that require information from multiple datasets. For example, a question assessing the risk of certain prescription medications among persons with certain conditions would require the use of physician billing data, hospitalizations and prescriptions. 
  • Analyses that are longitudinal: The Cohort is able to provide a provincial perspective of all overdose cases. Regional and sub-regional stratifications are possible which allows for an understanding of potential geographic differences throughout the province.
  • Analyses that are provincial in scope or require comparison between regions: The Cohort is able to provide a provincial picture of all persons who overdose on opioids. Regional and sub-regional stratifications are possible which allows for an understanding of potential differences throughout the province.
  • Evaluation of interventions to prevent overdose: Yearly updates to the cohort are planned. As the length of follow-up grows and new interventions are implemented, it will be possible to conduct evaluations of specific interventions to better understand their effectiveness.

For more overdose response knowledge summaries and reports, see Overdose Reports.

Limitations

The Cohort is not a surveillance tool as it does not have real-time information on overdose events. 

For up-to-date surveillance reports and tools, see the Overdose Data Dashboard

Only information contained in available administrative data sources can be interrogated. For instance, investigating employment histories prior to an overdose is not possible with currently available data sources.

SOURCE: Provincial Overdose Cohort ( )
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