Accuracy of external cause of injury codes reported in Washington State hospital discharge records.

OBJECTIVE: To evaluate the accuracy of external cause of injury codes (E codes) reported in computerized hospital discharge records.
METHODS: All civilian hospitals in Washington State submit computerized data for each hospital discharge to a file maintained by the Department of Health. In 1996, 32 hospitals accounted for 80% of the injury related discharges in this file; from these hospitals, we sampled 1,260 computerized records for injured patients in a stratified, but random, manner. An expert coder then visited the 32 study hospitals, reviewed the medical records that corresponded to each computerized record, and assigned an E code for that hospitalization. The computerized E code information was compared with codes provided by the expert reviewer.
RESULTS: The incidence of hospitalization for injury based upon computerized hospital discharge data was very similar to that based upon chart review: incidence rate ratio 1.0 (95% confidence interval 1.00 to 1.02). Computerized hospital discharge data correctly ranked injuries in regard to both mechanism and intent. Overall agreement on coding was 87% for mechanism of injury, 95% for intent of injury, and 66% for the complete E code. The sensitivity of computerized hospital discharge data for identification of falls, motor vehicle traffic injuries, poisonings, and firearm injuries was 91% or better. The predictive value positive of coding for these four categories of injury ranged from 88% for motor vehicle traffic injuries to 94% for poisonings. The amount of agreement for intent coding ranged from 84% for firearm injuries to 99% for falls. Agreement on coding of the complete E code ranged from 57% for firearm injuries to 72% for poisonings.
CONCLUSIONS: Computerized hospital discharge data can be used with confidence to determine how many injuries are treated in a hospital setting and the relative magnitude of various categories of injury. E codes reported in hospital discharge data are a reliable source of information on the types of information most often used for injury related analyses and priority setting. The detail codes (complete E codes) reported in hospital discharge codes are less reliable and must be used with caution.