Associated With the Automated Measurement of Mean Cell Hemoglobin Concentration in Dehydrated Cells

centrifuge and three different electronic cell counters in common laboratory use. For MCHC values above 36 g/dl as measured by the spun hematocrit method, all three electronic counters underestimated the MCHC, with increasing error as the true MCHC increased. For MCHC values below 30 g/dI. the values from two conductivity based instruments agreed with those from the spun hematocrit method. whereas one instrument based on light scattering overestimated the MCHC. These results indicate that inaccuracies in the measured mean cell volume (MCV) of dehydrated or otherwise undeformable cells may lead to spurious values for MCHC when electronic cell counters are used. I N THE initial evaluation of anemia, the mean cell volume (MCV) provides an important clue toward understanding the underlying cause of the anemia. Furthermore, because the electronic cell counters used in most clinical laboratories use the measured value of the MCV to derive the hematocrit and mean cell hemoglobin concentration (MCHC), the accuracy of these indices also depends on an accurate determination of the MCV. During the course of some experiments involving cells with very high MCHC, we became aware that MCHC values obtained from the electronic cell counter were significantly lower than those obtained from direct measurements of hemoglobin and spun hematocrit. Because the hemoglobin values were constant by the two methods, it was apparent that the discrepancy was in the values determined for the hematocrit. To investigate this problem further, we prepared a series of cell samples in which we varied over a wide range the water content of otherwise normal cells. We determined the MCHC of the samples using the spun hematocrit, as well as three popular electronic cell counters. We have found that for cells with very high MCHC, all three electronic counters substantially overestimated the MCV, thus giving a low value for MCHC. In addition, one electronic instrument maccurately measured the volume of swollen cells containing excess water. These results suggest that in the determination of red cell indices when appreciable deviation from normal MCV is suspected, alternative methods should be used to confirm values obtained from the electronic instruments.