Study objective: Duration of post-traumatic amnesia (PTA) is an important index of severity of head injury. Retrospective assessment of PTA duration is arguably unreliable. Existing objective measures of PTA duration are designed for use over a 24-hour timeframe and, therefore, are not useful for assessing PTA following mild head injury (MHI). A revised version of the Westmead PTA scale was developed for assessing patients with MHI in the Emergency Department (ED) at hourly intervals. The objective of this study was the field testing of this scale in EDs and assessment of validity and reliability of test items.
Methods: The scale contained 12 items, assessing orientation, memory for a face and name in a photograph and three pictures of objects. This revised scale, administered by nursing staff, was completed at least four times at hourly intervals by 147 adults with MHI in the ED and again at follow-up 1 week later. It was also completed by 109 demographically similar controls. Results were compared with Glasgow Coma scores and retrospective estimates of PTA duration based on patient report and medical records.
Results: Thirty-six per cent of MHI participants made errors on the scale in the ED, a significantly greater proportion than in MHI or controls at follow-up. Removal of the items 5 (day of week) and 9 (recall of name of face in photograph) improved the validity of the measure significantly. Scores correlated significantly with Glasgow Coma Scale scores and estimated duration of PTA.
Conclusion: The Westmead Scale (minus items 5 and 9) is a valid measure of PTA duration in adult patients with MHI in ED. Its use will allow for more appropriate timing of discharge and accurate prognostic information.