Background Hospital episode statistics (HES) and other health service utilisation data are based upon International Classification of Disease version 10 (ICD-10) diagnostic clinical codes used in relation to presentations to hospital. No previous studies have reported the validity of clinical coding in identifying patients who present with acute recreational drug toxicity.

Aim To determine the proportion of presentations with acute recreational drug toxicity that have been appropriately coded using the ICD-10 diagnostic coding system.

Design Retrospective review of diagnostic codes applied to acute recreational drug toxicity presentations.

Methods Presentations to the emergency department (ED) with acute recreational drug toxicity were identified for a 12-month period. Diagnostic codes applied to these presentations were obtained, and the proportion that were appropriate ‘acute recreational drug toxicity’ diagnostic codes was determined.

Results There were 484 presentations with acute recreational drug toxicity between 1 January 2008 and 31 December 2008. 145 (30.0%) presentations had one or more diagnostic code(s) relating to that presentation. Of these, only 64 (44.1% of all coded presentations; 13.2% of all ED presentations) had been coded with a primary ICD-10 code that related to acute recreational drug toxicity.

Conclusions This study highlights that acute recreational drug toxicity presentations are not appropriately coded within the currently available ICD-10 clinical diagnostic codes. Further work is needed to determine how acute recreational drug toxicity-related presentations are coded by clinical coders to determine the optimal method to ensure that the true burden of acute recreational drug toxicity is captured and adequate services are provided for this burden.