Performance evaluation of the Z2 coulter counter for WBC and RBC counting

The Z2 Coulter Counter (Z2) is a new, single-channel semi-automated electronic counter using the Coulter principle, providing both count and concentration results of cells, as well as providing size distribution of the cell population. The Z2 was evaluated according to guidelines published by the International Committee for Standardisation in Haematology. The results demonstrated excellent linearity for WBC and RBC (r > 0.999). The Z2 showed excellent precision, with a within-run, between-run and overall coefficient of variance less than 2%. Carryover was generally acceptable (<1%). WBC and RBC were stable after blood storage for 48 h at 4 degrees C and room temperature. There was almost no interference for WBC, RBC at high concentrations of bilirubin (178.5 mumol/l) or triglyceride (14.8 mmol/l) (P > 0.05). The bias of coincidence correction in WBC and RBC counting with the Z2 was less than 1%. Correlation between the Z2 and Sysmex F-820 or SE-9500 was excellent (r > 0.996) for WBC and RBC counting. Our results indicate that the Z2 has good features of precision, accuracy, linearity and good comparison with other haematology analysers, and could be used as a calibrating instrument for WBC and RBC counting.