Commentary

Although the studies by Haydel and Hoffman et al use somewhat different methods, they reach remarkably similar conclusions about the initial management of 2 important clinical problems in the ED: minor head injury and suspected (blunt) injury to the neck. In traditional practice, almost all patients with minor head injuries have CT, and those with suspected neck injuries have radiography of the cervical spine. The 2 studies show that for both conditions a small but important, clinically identifiable subset of patients can have imaging studies safely omitted.

The decision rules in both studies are based on a sufficiently large number of signs, symptoms, and other clinical attributes to guarantee essentially perfect sensitivity at the cost of very low specificity. Thus, the decision rules are typical screening instruments: they are most valuable in the context of high occurrence rates in busy EDs. In such settings, the systematic implementation of the decision rules in these 2 groups of patients may reduce imaging costs by approximately 20%.

Defensive physicians might argue that no decision rule is perfect. To guard against even the smallest risk for missing an occult intracranial haemorrhage or an unstable cervical fracture, they routinely order imaging procedures on all patients on the basis of the unspoken assertion that the risks and costs of the procedures are less than those of not ordering the tests. The 2 studies allow us to bracket the risks of omission. Taking a somewhat broader view, the quest for total certainty can actually negatively affect the health of a population. Healthcare budgets, however large, are limited; every additional procedure done implies that some other healthcare activity must be curtailed.¹ The studies allow us to identify patients in whom imaging would provide marginal cost benefits. Not ordering radiological procedures for patients identified by the decision rules as low risk, can improve, therefore the overall quality of health care.

3 potential applications of these studies immediately come to mind. Firstly, as clinical decision aids, they provide peace of mind for physicians torn between concern for patients and administrative demands for cost saving. Secondly, as auditing tools, they can identify potential areas in which to economise without sacrificing quality of care. Thirdly, they can serve as a safeguard against unjustified accusations of substandard care.

The rules are only as valid as the individual clinical items on which the decisions are based. Identification may be trivial for such items as age, headache, or vomiting. Some skill, however, may be required to elicit a history of antegrade amnesia, and a fair degree of clinical competence is needed to rule out the presence of minor focal neurological deficits. Institutions that plan to impose the use of decision rules to reduce the number of unnecessary investigations should ensure that clinical assessments are done at the required level of competence.

Neither of the studies explicitly addresses the role of patients' preferences to have imaging studies. Current concepts of clinical decision making and patient autonomy assert that patient preferences need to be respected.² Thus, the real challenge for ED physicians will be to convince patients that less is more.