- Red blood cell (RBC) histogram:
- RBC histogram is used to measure/calculate:
- RBC count
- Mean cell volume (MCV)
- Red cell distribution width (RDW)
- Most hematology analyzers use impedance to count and characterize RBCs, identified by volume cut-offs.
- Lymphocytes, the smallest of the white blood cell (WBC) subtypes, have a reported mean volume of:1
- 166 +/- 19.3 (range 126-216) fL in normal individuals
- 206 +/- 14.4 (range 126 +/- 246) in patients with CLL
- Some of the lymphocytes are small enough to be counted in the RBC gate.
- Normally, there are so few lymphocytes relative to the number of RBCs that they do not affect the results even if a few are included in the RBC analysis.
- In chronic lymphocytic leukemia (CLL), hyperleukocytosis may result in a bimodal population (RBCs and lymphocytes) resulting in an artificial elevation in the MCV (pseudo-macrocytosis) and RDW.
- RBC histogram is used to measure/calculate:
- Other red cell indices:
- Mean corpuscular hemoglobin (MCH) is calculated as hemoglobin/RBC count:
- Mean corpuscular hemoglobin concentration (MCHC) is calculated as Hb/Hct:
- The Hb is not affected by hyperleukocytosis.
- In most automated analyzers, the Hct is derived from the MCV and RBC count (Hct – RBC count x MCV).
- Because the MCV is disproportionally affected (increased) relative to a change in the RBC count, the MCHC is decreased in such cases.
