Clinical experience provides clinicians with an intuitive sense of which
findings on history, physical examination, and investigation are critical
in making an accurate diagnosis, or an accurate assessment of a patient's
fate. A clinical decision rule (CDR) is a clinical tool that quantifies the
individual contributions that various components of the history, physical
examination, and basic laboratory results make toward the diagnosis, prognosis,
or likely response to treatment in a patient. Clinical decision rules attempt
to formally test, simplify, and increase the accuracy of clinicians' diagnostic
and prognostic assessments. Existing CDRs guide clinicians, establish pretest
probability, provide screening tests for common problems, and estimate risk.
Three steps are involved in the development and testing of a CDR: creation
of the rule, testing or validating the rule, and assessing the impact of the
rule on clinical behavior. Clinicians evaluating CDRs for possible clinical
use should assess the following components: the method of derivation; the
validation of the CDR to ensure that its repeated use leads to the same results;
and its predictive power. We consider CDRs that have been validated in a new
clinical setting to be level 1 CDRs and most appropriate for implementation.
Level 1 CDRs have the potential to inform clinical judgment, to change clinical
behavior, and to reduce unnecessary costs, while maintaining quality of care
and patient satisfaction.