Automated WBC differential counters will identify only a limited number of cells but may do this very precisely and accurately. In a cancer center and in an orthopedic center, 10% and 6%, respectively, of all admissions will have circulating "abnormal" cells that might be missed by the automated instruments. Abnormal cells include blasts, promyelocytes, myelocytes, metamyelocytes, bands, reactive and immature lymphocytes and nucleated red cells. Eosinophilia and basophilia also have clinical implications. The argument is made that a screening method that fails to detect such cells may be inadequate and a simple practical solution is proposed. This will not eliminate the need for a stained smear but will reduce the call for a labor intensive manual differential count.
