Drug Overdose Case Definitions

VDH uses case definitions to identify suspected unintentional drug overdose emergency department (ED) visits. These definitions rely on discharge diagnosis codes and chief complaint (reason for visit) to classify a visit as overdose-related.

  • Discharge Diagnosis: Suspected overdose-related ED visits are identified using standard medical codes for clinical diagnosis and insurance billing purposes (ICD-9-CM, ICD-10-CM and SNOMED CT). In syndromic surveillance data these codes may be preliminary and may not specify the substance(s) involved in the suspected overdose.
  • Chief Complaint: Chief complaint is a text field describing why the patient came to the ED. The amount of information in the chief complaint can vary. Definitions include key terms and possible misspellings.

Additional notes:

  • Intent: The case definitions aim to capture suspect overdose ED visits of unintentional or undetermined intent. However, syndromic surveillance data do not include complete intent information. Some intentional overdose visits may be included.
  • Disposition: Disposition refers to the patient status at the end of the ED visit (e.g., discharged, admitted, deceased). Although ED visit data is sometimes referred to as “non-fatal” data, the case definitions do not include disposition status. It is possible that some overdose ED visits result in death.
Last Updated: January 30, 2026