ICD-10 codes detect only a proportion of all head injury admissions.

Despite criticism, the codes covering traumatic brain injury under the International Classification of Diseases have been widely used for sample collection in the epidemiological studies of head injury. Data have been collected from an Accident and Emergency department's (A&E's) case register on all head injury admissions to hospitals from a defined geographic area between 1 April 1996 and 31 March 1997, and compared with the list collected from the heath authority's central database by using the ICD-10 codes. Thirty seven per cent of the names in the A&E register appeared in the ICD-10 list, and 41% of the names in the ICD-10 list appeared in the list collected from the A&E department. The incidence of reported head injury was found to be three times higher among the 0-15 years age group compared with the 16-64 years age group (3.3% compared with 1% of the population). Among the 16-64 years age group, the peak rates of admission to hospital were in the months of February and August. Approximately 14% of all the head injury admissions stayed in hospital for more than 72 hours, another 14% stayed between 48 and 72 hours, and the rest (72%) stayed for less than 48 hours.