The interrelationships and stability of Coulter S-determined blood indices.

The blood of 104 medical inpatients was examined at various intervals during storage for 72 hours using a Coulter S counter. Over this period remarkable stability of the white cell count, red cell count, haemoglobin, and mean cell haemoglobin was demonstrated. This permits a useful interpretation of indices obtained in routine postal samples sent to the laboratory by general practitioners for screening. Furthermore, the implications of high correlations between red cell indices in freshly examined blood are considered and the regression line MCV = 2.5 MCH + 16 is derived. Using this relationship the normal range of the Coulter S MCHC is defined as 32.6-33.7 g/dl. The significance of the Coulter MCHC in present-day practice is reassessed and the importance of recognizing values for MCV and MCH not coinciding with the regression line is briefly discussed.