The influence of extraneous factors on Coulter S measurement of the mean corpuscular volume.

Alteration in the temperature of the Isoton diluent in a Coulter model S counter over a range of possible laboratory working temperatures produced a change in the mean corpuscular volume using EDTA and dipotassium acid citrate dextrose blood and a commercial control, 4C. Contamination of the Isoton diluent with hypochlorite solution, used to clean the Coulter model S, may increase the mean corpuscular volume of EDTA blood without altering other measured parameters. Attention to both these points is required in assessing quality and calibrating the machine.