Total and differential leukocyte counts in clinically well children. Information or misinformation?

To determine whether the total and differential leukocyte count is of value as a case-finding test, we applied the evaluation criteria developed by the US Preventive Services Task Force. The criteria comprise review of the current burden of suffering of the disease to be prevented, the attributes of the intervention to be used, and the quality of the evidence available. A literature search revealed no evidence in the form of data from patients, so a chart review of all complete blood cell counts ordered during a 1-year period by one group of pediatricians was undertaken. At least one value outside of published normal ranges was found on 74.7% of the tests performed on clinically well children. No unsuspected illness was discovered as a result of an abnormal total and differential leukocyte count.