Data linkage of healthcare services: Alcohol and drug ambulance attendances, Emergency Department presentations and hospital admissions (2004-09)

Background: To examine the feasibility of linking individual records from three siloed health data sources, drawn from Victoria, Australia: data relating to drug and alcohol ambulance attendances, and associated emergency department presentations and hospital admissions. Methods: The cohort for data linkage consisted of all patients attended by ambulance for alcohol- and other drug-related events in metropolitan Melbourne, Victoria, from 01 July 2004 to 30 June 2009. Three population-level administrative datasets were linked using the deterministic approach for matching: ambulance records, emergency department presentations, and hospital admissions. The linkage of these datasets involved a series of processes designed to maximise the number of cases linked and minimise the risk of incorrectly linked unrelated cases. Results: Of the 97,433 drug and alcohol ambulance attendances for the 2004-05 to 2008-09 period, 69,912 (over 70%) of these were reported as being transported to an emergency department. We linked approximately 90% of transported ambulance cases with emergency department data. We then identified 25% of these cases as being admitted to hospital. Conclusion: These results are a cornerstone for future studies examining the pathways of care associated with drug and alcohol ambulance attendances. Exploration of these linked data will provide an excellent opportunity to examine the nature and extent of drug- and alcohol-related harms across acute care settings, and enhance the capability of the available data to identify involvement of alcohol and drugs.