1. Buffy coat (leukocytes and platelets) - <1%
How to Read a CBC
Measure of formed elements:
Red blood cells
White blood cells
Platelets
Additional information:
Hemoglobin
Hematocrit
RBC size/shape
WBC Differential
Always check norms for age!!
Plasma –
55% of whole blood
Erythrocytes –
45% of whole blood
Buffy coat (leukocytes and platelets) - <1%
The CBC measures the formed elements in the blood, including red blood cells, white blood cells and platelets. It also contains valuable additional information about hemoglobin and hematocrit, red cell size and shape, and the white blood cell differential count. We will review all of these in detail.
It is important, when reviewing CBC results, to use age-specific norms for your patient and NOT “adult” values. If you lab does not include pediatric norms as reference values with the CBC report, you should use outside references, such as a pediatric textbook or the Harriet Lane Handbook, to determine the normal values for your patient’s age.
Description of picture:
The tube shows what happens to blood after it is drawn and “spun down”. Red cells fall to bottom, plasma to the top. The thin layer between the 2 regions is the buffy coat and is where the WBCs and platelets are found.
Illustration by Devika Bhatia, 2003.
© APON 2003

2. Red Blood Cell Assessment
RBC count
total # of RBCs in each cc of blood
Hemoglobin
iron-rich protein found inside RBCs, measured in gm/dl
indicator of O2-carrying capacity
Hematocrit
% of RBC’s by volume
There several indicators for assessing Red Blood Cells on the CBC, including:
Red Blood Count (RBC) is the total number of RBCs in each cc of blood
The Hemoglobin is the iron-containing pigment of RBCs, measured in gm/dl, and is an indicator of the oxygen-carrying capacity of the blood
The Hematocrit is the percentage of RBCs relative to plasma volume
Illustration by Devika Bhatia, 2003.
© APON 2003

3. Red Blood Cell Assessment: Size & Color
MCV (mean cell volume)
RBC size
MCH (mean cell hemoglobin)
MCHC (mean cell hemoglobin concentration)
RBC hemoglobin content (color)
RDW (red cell distribution width)
Variation in RBC size
The RBC indices are useful for assessing the size and color of the red blood cells:
MCV (mean cell volume) indicates red cell size
MCH (mean cell hemoglobin) indicates amount of hemoglobin in each RBC
MCHC (mean cell hemoglobin concentration) indicates the concentration of hemoglobin per RBC (related to the hydration status of the RBC)
MCH and MCHC are both indicative of RBC color (pale vs. normal)
RDW (red cell distribution width) indicates variations in the size of RBCs
© APON 2003

4. Platelet Count Platelets plug holes in damaged blood vessels
prevent bleeding
Platelets:
Small disc-shaped cells, important in controlling bleeding by plugging damaged vessels.
© APON 2003

5. White Blood Count White blood cells: Fight infection Make antibodies
Several subtypes of WBCs make up the “differential count”
Lymphocyte
Neutrophil
Platelet
White Blood Count (WBC)
White blood cells have several functions including fighting infection and making antibodies. There are several types of WBC that can be observed in the peripheral blood. When a CBC is done, a drop of blood is placed on a microscope slide and stained. The slide is then observed under the microscope and the various types of white blood cells described in the “differential” count.
© APON 2003

6. WBC Differential
Assesses percentage of each different subtype of WBC in blood
Reported as % of total cells counted
% of all types reported should add up to 100
Eosinophil
Neutrophil
Band
Lymphocyte
Monocyte
The WBC differential count measures the relative proportion of each different type of WBC in the blood.
100 WBCs are usually counted. The total of each WBC type is reported as a percentage of the total number of WBCs. The percentage of all types together should add up to 100.
Illustration by Devika Bhatia, 2003.
© APON 2003

7. WBC Differential: Types of Cells
Neutrophils (infection-fighters)
segs or polys (mature)
bands or stabs (young)
Lymphocytes (immunity)
Monocytes (phagocytosis)
Eosinophils (allergy, parasites)
Basophils (hypersensitivity)
Blasts (very immature)
(Blasts should ALWAYS be considered ABNORMAL unless proven otherwise)
Lymphocyte
Neutrophil
Monoocyte
Blasts
Types of WBCs normally present in blood:
- neutrophils (infection-fighters), 2 types:
 polys or segs = segmented neutrophils (mature)
 bands or stabs = banded neutrophils (young)
- lymphocytes (immunity)
- monocytes (phagocytosis)
- eosinophils (allergy, parasites)
- basophils (hypersensitivity)
Blasts are very immature WBC’s. If there are blasts reported on a CBC, this is always considered abnormal until proven otherwise!!!
In neutropenia, most WBCs are lymphocytes. An early indication of recovery is the presence of monocytes,
Non-malignant blasts are sometimes seen during neutrophil recovery following chemotherapy, especially in conjunction with GCSF/GMCSF therapy, as a result of an over stimulated bone marrow releasing immature cells into the peripheral circulation.
© APON 2003