DESCRIPTION AND VALIDATION OF A FLOW-CYTO METRIC METHOD TO ESTIMATE WHITE BLOOD-CELL COUNTS IN LEUKOCYTE-DEPLETED RED-CELL CONCENTRATES

We describe a flow-cytometric method for estimating residual white blo od cells (WBC) counts in WBC depleted blood components, namely units o f packed red cells. The method uses fluorescent staining of nuclear AD N with ethidium bromide. WBC nuclei are discriminated from background events using fluorescence ratio (585 nm versus 650 nm). A facultative procedure of concentration is described, in order to get better sensit ivity at very low WBC counts. Main steps of validation are dilution as says and correlation with hemocytometer counts. The method can be used to explore very low concentrations (less than 100 WBC/ml) and should be useful in quality control of blood products.