Background: Hospital discharge data (HDD) represent one of the most valuable information sources for injury prevention and control.
Objectives: To investigate external code of injury (E-code) underreporting in the Finnish National Hospital Discharge Register from 1 January 1987 to 31 December 2004.
Material and methods: HDD for discharges with an injury as the main diagnosis were extracted from the FNHDR. The selection was made using codes for nature of injury (1987-1995, ICD-9; 1996-2004, ICD-10). The proportion of injury discharges with a missing E-code was examined by sex, age, hospital districts, type of hospital, duration of hospitalization, and nature of injury.
Results: In 432,549 (23.1%) of the recorded 1,868,519 discharges, an E-code was missing. The proportion of the discharges with a missing E-code varied among the above variables. During the period 1987-2004, the overall E-code underreporting decreased from 18.0% to 12.8%. The introduction of the ICD-10 in 1996 was followed by a dramatic increase (up to 57.5% of all discharges) in E-code underreporting.
Conclusions: More attention ought to be dedicated to teaching and periodic training on the use of E-codes. Educational activities should specifically target the medical doctors, who, in Finland, are responsible for assigning the E-codes.