Coulter counter model S and model S-plus measurements of mean erythrocyte volume (MCV) are influenced by the mean erythrocyte haemoglobin concentration (MCHC)

Abstract

We found differences between the mean erythrocyte volume (MCV) when measured by the Coulter counter model S-plus and when calculated from the erythrocyte volume fraction obtained by centrifugation and corrected for trapped plasma. The difference was positively correlated to the mean erythrocyte haemoglobin concentration (MCHC) so that MCV by the Coulter S+ is too low at low MCHC and too high at high MCHC. Similar although smaller differences were observed with the Coulter S. The erroneous MCV gives errors in the calculated erythrocyte volume fraction and MCHC. Only in the case of MCHC does the error have any practical significance; too high values are obtained at low concentrations of haemoglobin in the erythrocytes and too low at high concentrations. Hence, MCHC measured by the Coulter S+ contains no useful information.

Key Words:

• electronic cell counters
• mean cell haemoglobin concentration
• mean cell volume