Completeness and accuracy of International Classification of Disease (ICD) external cause of injury codes in emergency department electronic data

The accuracy of external cause of injury codes (E codes) for work‐related and non‐work‐related injuries in Massachusetts emergency department data were evaluated. Medical records were reviewed and coded by a nosologist with expertise in E coding for a stratified random sample of 1000 probable work‐related (PWR) and 250 probable non‐work‐related (PNWR) cases. Cause of injury E codes were present for 98% of reviewed cases and accurate for 65% of PWR cases and 57% of PNWR cases. Place of occurrence E codes were present in less than 30% of cases. Broad cause of injury categories were accurate for about 85% of cases. Non‐specific categories (not elsewhere classified, not specified) accounted for 34% of broad category misclassifications. Among specified causes, machinery injuries were misclassified most often (39/60, 65%), predominantly as cut/pierce or struck by/against. E codes reliably identify the broad mechanism of injury, but inaccuracies and incompleteness suggest areas for training of hospital admissions staff, providers, and coders.