Automated hematology: where we stand.

Rapid, accurate, and relevant laboratory testing is essential in an era of cost-effective medicine. The routine manual complete blood count (CBC) is a labor-intensive test that lacks reproducibility. The new automated instruments such as the Coulter S+ series offer "state of the art" precision and accuracy in counting more than 10,000 cells per blood sample. The nonoptical electronic impedance method yields RBC, WBC, and platelet data, as well as histograms that characterize hematologic data. Analysis of more than 3,500 cases yielded a false-negative rate of less than 4% and a false-positive rate of 30%, indicating the instrument's accuracy in recognizing and flagging abnormalities. All normal screened CBCs were free of significant abnormalities. The Coulter S+ series provides innovative parameters and histograms that aid in establishing differential diagnoses. We review the advantages and the limitations of automation. Morphologic examination of abnormal blood smears remains the cornerstone of diagnosis in both the new and the old hematology.