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The authors have assessed the clinical value of an "accurate" band count as a correlate to infection in 33 patients with a culture proven bacterial infection and a normal total leukocyte count. Thirty hematologically normal outpatients, presumably with no infections, were selected for the control group. Manual 500 cell differentials were performed on each subject in both groups. The absolute and percent band count, the absolute and percent total neutrophil count, and the presence of neutrophils more immature than bands were analyzed for their ability to identify the patients with an infection. The presence of neutrophils more immature than bands and the absolute neutrophil count are the two values that best separated the infected patients from the outpatients, even though the selected patients had a normal total leukocyte count. The band count had minimal value for identifying infected patients. Other studies were reviewed regarding the utility of band counts. The authors conclude that manual band counts are unnecessary because when accompanied by a clinical assessment of the patient, automated instruments accurately provide the appropriate hematologic data that may aid in the diagnosis of infection.

This article explores the analytical inaccuracies of routinely performed leukocyte differentials and cites the known biologic and personal physiologic variability in the total leukocyte counts and the leukocyte differential. The clinical value of leukocyte differentials in patients without hematologic disease is assessed on the basis of reports in the existing medical literature. It is concluded that the 100- or 200-cell differential is of no value in the majority of patients on whom the test is requested and that an initial scan of 300 or more cells in concert with the 10,000-cell differentials now available from instruments will soon replace the traditional " diff ".

A strategy for the use of the newer technology for automated leukocyte differential counting is proposed. The design of the system is felt to be cost effective, yet guarantees that patients with mild or early stages of potentially serious hematologic diseases will not be missed. A key feature of this system is a rapid visual scan of the blood film by an expert morphologist. Implementation of this system should permit significant reductions in personnel as well as reagents and other supplies.

2 cases of acute leukaemia in which the precise diagnosis was established using the immunoperoxidase technique on particle sections, a method not usually employed for acute leukaemias, are reported. Morphologically and cytochemically these cases were initially diagnosed as acute megakaryoblastic (case 1) and acute monocytic (case 2) leukaemia. Based on the immunoperoxidase studies, these diagnoses were corrected to DiGuglielmo's disease (case 1) and plasma cell leukaemia (case 2).

Hematocrit determinations by microhematocrit and electronic particle counter technics were obtained using newborn and adult blood samples. Coulter Model S hematocrit values greater than .47 were found to be significantly lower than those obtained by using the microhematocrit technic. These differences assume clinical importance when considering partial plasma exchange transfusion for the treatment of polycythemia and associated hyperviscosity.