THE HEMALOG D WHITE CELL DIFFERENTIAL SYSTEM

The Hemalog D system performs automated differential white cell counts utilizing principles of cytochemistry, electro-optical measurement and signal logic processing. Using 0.4 ml of anticoagulated whole blood and an automated continuous flow staining technique, the system is designed to process a new sample each minute. The decision logic classifies individual cells by size and intensity of staining as they flow through detectors designed to measure light loss and light scattering simultaneously. With this system, 10,000 cells/ sample are classified in less than 1 min. Alcian Blue identifies basophils when used in the presence of quaternary ammonium salts and other counterions. Monocytes are the only cells stained in an esterase method using α-naphthol butyrate at pH 6.1 with hexazonium pararosanilin as coupler. This unstable diazonium is produced on stream continuously from stable components. Size and peroxidase staining serve to classify the remaining cells. Lymphocytes and large mononuclear cells are unstained, neutrophils have moderate peroxidase activity, while eosinophils stain very strongly. Threshold detection logic for light scattering and absorption differentiate the neutrophils, eosinophils and lymphocytes. The distribution of peroxidase activity in neutrophils serves as an index of maturity of these cells. The clinical evaluation of this index is reported elsewhere. Results are reported as percentage and as cells per cubic millimeter. A total white blood cell count is also reported and the pattern of cell measurements for 10,000 cells is provided as a picture with diagnostic information content. Advantages of this system in rapid screening result from improved precision of automation, the processing of large numbers of cells and the saving of labor. Precision also makes the acquisition of sequential data on single patients more meaningful and diagnostically valuable.