AUTOMATIC VOLUMETRIC CAPILLARY CYTOMETRY FOR COUNTING WHITE CELLS IN WHITE CELL-REDUCED PLATELETPHERESIS COMPONENTS

BACKGROUND: As the benefits of white cell (WBC)-reduced blood componen ts become increasingly apparent, the need has arisen for a simple, aut omated WBC-counting technique that is sensitive to tow WBC concentrati ons. Automated Volumetric capillary cytometry was evaluated for its ab ility to quantify residual WBCs in WBC-reduced platetetpheresis compon ents. STUDY DESIGN AND METHODS: The volumetric capillary cytometry sys tem evaluated uses a laser to excite fluorescent dye-labeled nucleated cells. The number of nucleated cells per mu L is reported. Four studi es were performed: linearity, precision of results near the value of 5 x 10(6) WBCs per unit, the limit of detection, and correlation to the Nageotte manual counting method. RESULTS: Assay Values correlated to expected values (range, 0-125 WBC/mu L) with an r(2) >0.99. In the ran ge of 5 x 10(6) WBCs per unit, the CV was 8.5 percent, and concentrati on differences of 0.15 log(10) were detectable. The limit of detection was 1.0 WBCs per mu L (95% upper confidence limit). The assay correla ted to the Nageotte method with an r(2) of 0.98, slope of 1.0, and y-i ntercept of 2.0 WBCs per mu L. Assay results were 10 to 15 percent hig her than Nageotte results, in samples with values near 5 x 10(6) WBCs per unit. Technician time per sample was 2 to 3 minutes. CONCLUSION: V olumetric capillary cytometry is precise and sensitive to small differ ences in WBC concentration in the range of clinical interest. The devi ce provides an efficient new method for quality assurance and control of WBC-reduced plateletpheresis products.