CBC Flashcards
A CBC is typically performed using
an automated instrument that measures various parameters, including cell counts and the physical features of some of the cells.
A standard CBC includes the following
Red blood cell (RBC) count
is a count of the actual number of red blood cells in your blood sample.
Hemoglobin
measures the total amount of the oxygen-carrying protein in the blood, which generally reflects the number of red blood cells in the blood.
Hematocrit
measures the percentage of your total blood volume that consists of red blood cells.
Red blood cell indices provide information on the physical features of the RBCs:
Mean corpuscular volume (MCV) is a measurement of the average size of your red blood cells.
Mean corpuscular hemoglobin (MCH) is a calculated measurement of the average amount of hemoglobin inside your red blood cells.
Mean corpuscular hemoglobin concentration (MCHC) is a calculated measurement of the average concentration of hemoglobin inside your red blood cells.
Red cell distribution width (RDW) is a measurement of the variation in the size of your red blood cells.
The CBC may also includereticulocyte count
which is a measurement of the absolute count or percentage of newly released young red blood cells in your blood sample.
White blood cell tests
> White blood cell (WBC) count
is a count of the total number of white blood cells in your blood sample.
White blood cell differential
may be included as part of the CBC or may be done in follow up if the WBC count is high or low. The WBC differential identifies and counts the number of the five types of white blood cells present (neutrophils, lymphocytes, monocytes, eosinophils, and basophils). The individual count can be reported as an absolute count and/or as a percentage of total.
Platelet tests
platelet count
Mean platelet volume (MPV)
Platelet distribution width (PDW)
platelet count
the number of platelets in your blood sample
Mean platelet volume (MPV)
may be reported with a CBC. It is a measurement of the average size of platelets.
Platelet distribution width (PDW)
may also be reported with a CBC. It reflects how uniform platelets are in size.
CBC results that are outside the established reference intervals may indicate
the presence of one or more diseases or conditions. Typically, other tests are performed to help determine the cause of abnormal results.
Red blood cell indices
mean cell volume(MCV)
mean cell hemoglobin(MCH)
mean cell hemoglobin concentration(MCHC)
These indices can be calculated from the hemoglobin, hematocrit, and red blood cell count valuesalthough on automated analyzers, the MCV is usually measured directly.
mean cell volume(MCV)
A complete blood count includes measurements of the three red blood cell indices
mean cell hemoglobin(MCH)
The average size of red blood cells, expressed in femtolitres
mean cell hemoglobin concentration(MCHC)
The average amount of hemoglobin per red blood cell, expressed in picograms
RBC indices and anemia
Evaluation of red blood cell indices is helpful in determining the cause of anemia
microcytic anemia
Anemia with a low MCV
macrocytic anemia
Anemia with a high MCV
hypochromic anemia
Anemia with a low MCHC
normochromic anemia
If anemia is present but the red blood cell indices are normal
An elevated MCHC can also be a false result from
conditions like red blood cellagglutination (RBC clumping)
(which causes a false decrease in the red blood cell count, elevating the MCHC).
Red blood cell distribution width
- The red blood cell distribution width (RDW) reflects the degree of
variation in size of red blood cells. - An elevated RDW represents increased variation in red blood cell
size, a condition known asanisocytosis. - Elevated RDW can be due to nutritional anemiassuch asiron
deficiency anemiaand anemia due toVitamin B12 - A low RDW has no clinical significance.
