Factors producing error in the total leucocyte count as measured on the Coulter Counter S Plus IVD.

Whole blood specimens, anticoagulated with potassium EDTA, which were seen to have particles interfering with the total leucocyte count were collected. This interference was detected, when the samples were processed through a Coulter Counter S Plus IVD, by R1 regional flags or backlighting of the leucocyte count. These specimens then had visual leucocyte counts performed using a counting chamber method and were examined microscopically, to ascertain possible causes of the interference. It was shown that the degree of error in the leucocyte count produced varies considerably but can be very high. Particles causing the error were found to include fibrin strands, platelet clumps, nucleated red cells and giant platelets.