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Toronto Notes 2019 Basics of Hematology
• over 1011 blood cells are produced daily
• sitesofhematopoiesisinadults:pelvis,sternum,vertebralbodies,andcranium • lifespanofmaturecellsinblood
■ erythrocytes (90-120 d), neutrophils (~1 d), platelets (7-10 d), lymphocytes (varies – memory cells persist for years)
• roleoflymphoidorgans
■ spleen: part of reticuloendothelial system, sequesters aged RBCs, removes opsonized cells, and site
of antibody production
■ thymus: site of T-cell maturation and involutes with age
■ lymph nodes: sites of B and T-cell activation (adaptive immune response)
Hematology H3
Complete Blood Count
Table 1. Common Terms Found in the CBC
To estimate Hb based on the Hct, multiply by 3.3
Clinical Use of RDW
To distinguish the etiologies of microcytosis:
• Iron deficiency: increased RDW
(anisocytosis) as cells are of varying sizes
in iron deficiency
• Thalassemia minor: normal RDW (also
expect a high RBC count) as cells are of similar size due to genetic defect in Hb
Test
Red Blood Cell (RBC) Count Hemoglobin (Hb)
Hematocrit (Hct)
Mean Corpuscular Volume (MCV) Mean Corpuscular Hb (MCH) Concentration (MCHC)
RBC Distribution Width (RDW) White Blood Cell (WBC) Count WBC Differential
Platelet Count
Mean Platelet Volume (MPV) Reticulocytes
*Normal values may vary depending on site and age
Definition
The number of RBCs per volume of blood
Amount of oxygen-carrying protein in the blood
Percentage of a given volume of whole blood occupied by packed RBCs
Measurement of RBC size
Amount of oxygen-carrying Hb inside RBCs
Average concentration of Hb inside RBCs
Measurement of variance in RBC size
The number of WBCs per volume of blood
Neutrophils Lymphocytes Monocytes Eosinophils Basophils
The number of platelets per volume of blood Measurement of platelet size
Immature RBCs that contain no nucleus but have residual RNA
Normal Values*
4.2-6.9 x 106/mm3
130-180 g/L (male) 120-160 g/L (female)
45%-62% (male) 37%-48% (female)
80-100 μm3
27-32 pg/cell 32%-36% 11.0%-15.0% 4.3-10.8 x 109/mm3
1.8-7.8 x 103/mm3 0.7-4.5 x 103/mm3 0.1-1.0 x 103/mm3 0.0-0.4 x 103/mm3 0.0-0.2 x 103/mm3
150-400 x 109/mm3
7.2-11.7 fL
Normally make up 1% of total RBC count
Approach to Interpreting a CBC
1. consider values in the context of individual’s baseline:
■ up to 5% of population without disease may have values outside “normal” range
■ an individual may display a clinically significant change from their baseline without violating
“normal” reference range
2. is one cell line affected or are several?
■ if all lines are low: pancytopenia (see Pancytopenia, H8)
■ if RBCs and platelets are low: consider a MAHA/TMA (see Microangiopathic Hemolytic Anemia/
Thrombotic Microangiopathy, H22)
■ if single cell line affected: see Common Presenting Problems, H6
Blood Film Interpretation
RED BLOOD CELLS
Size
• microcytic(MCV<80μm3),normocytic(MCV=80-100μm3),macrocytic(MCV>100μm3) • anisocytosis:RBCswithincreasedvariabilityinsize(increasedRDW)
■ iron deficiency anemia, hemolytic anemias, myelofibrosis, blood transfusion, and MDS
Colour
• hypochromic:increaseinsizeofcentralpallor(normal=lessthan1/3ofRBCdiameter) ■ iron deficiency anemia, anemia of chronic disease, and sideroblastic anemia
• polychromasia:increasedreticulocytes(pinkish-bluecells) ■ increased RBC production by bone marrow
Shape
• poikilocytosis:increasedproportionofRBCsofabnormalshape
■ iron deficiency anemia, myelofibrosis, severe B12 deficiency, MDS, and burns