Utility of the three-part leukocyte differential count

The utility of the automated three-part leukocyte differential count was evaluated in an acute care hospital setting. The manual method was specified in 92 of 223 (41%) requests for differentials on one day. For the others, 79 three-part differentials (60%) were completed; 19 (15%) were rejected for histogram abnormalities ("R-flags") or could not be computed; and 33 (25%) were rejected for out-of-range values that were later verified by slide review. The automated method missed 4 of 39 (10%) band elevations and 2 of 2 (100%) cases of eosinophilia reported on manual differentials, but those results had no apparent influence on patient management. In 98 cases of septicemia, automated and manual methods showed similar overall sensitivity (87% and 83%, respectively). Selectively combined with a qualitative slide review, the three-part differential was applicable to 84% of all specimens submitted for a differential count, with acceptable sensitivity and accuracy and substantial savings in personnel time.