Here are data showing a time-dependent increase in the mean cell volume when blood is stored at room temperature:
Note the increase in MCV of about 5 fL in 30 hours!
What is happening to the mean corpuscular hemoglobin concentration (MCHC) during this time?
Summary of the effect of storage time on red cell indices:
What happens to the hemoglobin and hematocrit over time with storage?
In a previous slide, we considered the change in mean corpuscular hemoglobin concentration (MCHC) from a descriptive standpoint – water enters cells, dilutes Hb. Now let’s formalize the concept with an equation:
MCHC = Hb/Hct
- Hb is unchanged
- Hct is decreased
- Thus, MCHC must decrease
Sort the CBC parameters (top) according to the changes occurring over time with blood storage (bottom):
Let’s switch gears and consider cold agglutinins
Below are schematics of red blood cell counting in an automated analyzer from a normal individual (left) and from a patient with cold agglutinin disease (CAD; right):
What happens to the red blood cell count in CAD?
Sort the CBC parameters (top) according to the changes that occur with cold agglutinins (bottom):
Hopefully you recalled in the last sorting exercise that the Hct is artifactually decreased in cold agglutinin disease (CAD).
Here is a very cool figure showing red cell distribution width (RDW) in a patient with cold agglutinin disease with blood incubated at various temperatures:
Now let’s consider hyperglycemia and hypernatremia. Sort the CBC parameters (top) according to the changes that in these conditions (bottom):
Check out these data!
What do you predict is happening to the hematocrit in the three samples above that were run on the automated analyzers?
You will note that the MCV (previous slide) and Hct (this slide) do not change with the spun Hct.
Why doesn’t the Hct change in the spun Hct?Click for Answer
Let’s look at a case:
Note how the red cell indices correct with normalization of the blood glucose level!
Here is another case of hyperglycemia-associated macrocytosis:
Which RBC best describes the phenotype in hyperglycemia or hypernatremia when measured in vitro (as part of a complete blood count [CBC])?
46 year-old male presented with hyperleukocytosis and leukostasis, found to have acute lymphoblastic leukemia, treated with leukapheresis.