Determining witnessed status for out-of-hospital cardiac arrest

The determination of witnessed status in out-of-hospital cardiac arrest may be challenging, as evidenced by the discrepancies in witnessed status when comparing different sources of information. The large number of cases where the witnessed status could not be determined from the emergency dispatch recording precludes its use as the sole source of information. It is reasonable to use the patient care record alone, however it should be recognized that there is misclassification of witnessed status regardless of the method used and this may affect the strength of association between witnessed status and survival.