Investigations may not change your patient’s management plan for several reasons. In some cases, the patient’s pre-test probability for a condition is low, and further testing is not necessary (e.g., screening for breast cancer in younger women with low risk of breast cancer). Another example is unnecessary preoperative testing before a low-risk surgical procedure where the risk of complications is low. On the other hand, high-risk patients may warrant treatment irrespective of the test result; thus, testing in these patients would not influence the ultimate decision to treat (e.g., thrombophilia testing in patients with an unprovoked pulmonary embolism at high risk for recurrence is not helpful, since these patients should receive indefinite anticoagulation). Where possible, residents can refer to evidence-based clinical decision rules to guide appropriate testing or treatment – examples include the Well’s criteria or pulmonary embolism rule-out criteria (PERC) for pulmonary embolism, the Canadian CT Head Rule for CT scan of the head in a trauma patient, or the Centor criteria for likelihood of bacterial infection in adult patients with a sore throat.
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