An automated blood smear analysis system. Clinical experience and performance

A detailed clinical evaluation of the diff3 system for examining peripheral blood smears was performed over a six-month period in a service hematology laboratory in a large teaching hospital. The diff3 automatically classifies 11 categories of nucleated cells; qualitatively evaluates erythrocyte size, shape, and color; estimates platelet and leukocyte count; and generates a quantitative estimate of platelet number. The analyzer contains a system for signaling abnormal or suspicious slides for technologist review. As many as 14 slides can be processed in sequence without operator attendance. Throughput averages 33 slides/hour in no review mode. The analyzer produced similar in-run and day-to-day precision when examining a wide variety of blood smears. Morphologic evaluation of nucleated and non-nucleated blood cells correlated with that of technologists. The diff3's normal range compared closely with that obtained by senior technologists examining conventional smears. Band counts, while somewhat higher, did not lead to judgement errors in left-shift direction. The diff3's sensitivity to recognizing abnormal smears was virtually identical to that of technologists with a false-positive level only slightly greater than theirs; diff3's false negatives were equal in frequency to those experienced by technologists.