Canadian CT head rule study for patients with minor head injury: Methodology for phase II (validation and economic analysis)

Prospective validation on a new set of patients is an essential test of a n ew decision rule. However, many clinical decision rules are not prospective ly assessed to determine their accuracy, reliability, clinical sensibility, or potential impact on practice. This validation process is important beca use many statistically derived rules or guidelines do not perform well when tested in a new population. The methodologic standards for a validation st udy are similar to those described in the article on phase I for derivation studies in the August 2001 issue of Annals of Emergency Medicine. The goal of phase II is to prospectively assess the accuracy, reliability, and acce ptability of the decision rule in a new set of patients with minor head inj ury. This will determine the clinical utility of the rule and is essential if such a rule is to be widely adopted into clinical practice.