Background: Each year, nearly 100 deaths and more than 10,000 admissions to Norwegian hospitals can be attributed to acute poisoning from non-medical substances and drugs in supra-therapeutic doses. The aim of this study was to evaluate hospitals' routines for coding of acute poisoning deaths and to provide information on the toxic agents involved.
Material and methods: Medical records of deaths (at 6 Norwegian hospitals in the period 1.1.1999 -31.12.2005) due to acute poisoning were re-examined to assess accuracy of diagnosis codes.
Results: Acute poisoning was registered as the cause of 225 deaths in the study period. The re-evaluation concluded that 45 of these deaths had other causes. In 125 of the remaining 180 deaths, acute poisoning was only registered as a side diagnosis, although re-examination revealed it was the major contribution to death in 66 % (83 of 125) of cases. The hospitals had classified the drugs according to ATC codes in 16 % (28 of 180) of patients with acute poisoning.
Interpretation: The present Norwegian coding practice does not document acute poisoning deaths in hospital correctly, and registry studies based on diagnosis codes should be interpreted with care. Current registration of poisoning agents' ATC-codes is insufficient and the Norwegian version of ICD-10 alone is not suitable for classification of acute drug poisoning. Replacement of the Norwegian ICD-10 version by the original international version should be considered and/or the routines for registration of ATC-codes should be improved.