• blood components;
  • flow cytometer;
  • leucocytes;
  • microvolume fluorimetry

Background and Objectives Accurate determination of residual leucocytes [white blood cells (WBC)] in blood components is of high clinical importance. To date, several labour-intensive, time-consuming or expensive techniques have been used for this purpose.

Materials and Methods A method for the determination of residual WBC is described using a novel low-cost flow-cytometric cell counter and analyser (CCA). The DNA in WBC was stained using 4′-6-diamidino-2-phenylindole (DAPI) and WBC were automatically analysed by true volumetric counting of 200-µl samples (prepared from a 20-µl undiluted sample).

Results Dilution experiments over a range of 0·5–50 WBC/µl showed a linearity of r= 0·998. The detection limit of this method was 0·83 WBC/µl of red blood cell concentrate (RCC) and 0·67 WBC/µl of platelet concentrate (PC), with an accuracy of 95·5%.

Conclusion Residual WBC (< 1 WBC/µl) can be accurately counted using the CCA within 2 min and at a total cost of less than € 1 per sample.