The document discusses components of a complete blood count (CBC) including: 1. Erythrocytes (red blood cells) characterized by hemoglobin concentration, red blood cell count, mean cell volume, and other measures. 2. Leukocytes (white blood cells) characterized by white blood cell count and differential. 3. Thrombocytes (platelets) characterized by platelet count. The CBC describes the tri-lineage of hematopoiesis including the erythroid, leukocyte, and thrombocyte lineages. Key information and interpretations of CBC results are provided such as distinguishing between microcytosis caused by iron deficiency versus thalassemia trait.

1. Complete Blood Counts (CBC)
Abdul-Kader Souid
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The erythrocytes, leukocytes & thrombocytes

2. CBC Describes the Tri-lineage Hematopoiesis
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Erythrocytes (red cells):
(1) Hemoglobin (Hb) concentration (g/L)
(2) Red blood cell (RBC) count (# of cells x1012/L)
(3) Reticulocyte (Retic) count (# of cells x109/L)
(4) Mean cell volume (MCV, fL) & Relative
distribution width (RDW = SD/MCV, %)
Leukocytes (white cells):
(5) White blood cell (WBC) count (# of cells x109/L)
(6) WBC differential = neutrophil, lymphocyte,
monocyte, eosinophil, and basophil counts (# of cells x109/L)
Thrombocytes (platelets):
(7) Platelet count (# of platelets x109/L)
2
Reticulocytes
Tri-lineages Hematopoiesis

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1. Normal leukocyte and platelet
lineages.
2. Erythroid lineage:
Microcytosis (low MCV),
normal RDW and high RBC
count, consistent with
thalassemia trait.
3. Hematocrit, MCH, and
MCHC are calculated values.
4. MPV = mean platelet volume.
CBC in an 8-year-old girlWBCdifferential

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Hemoglobin Concentration
varies with age and gender
Lower Limits (-2SD) of Normal Hemoglobin Concentrations (g/L)
Birth 145
(↑due to low fetal oxygen)
2 to 6 mo 90
(physiologic anemia)
4 to 12 y 115
(pre-pubertal)
12-18 y (males) 140
(male puberty hormones)
12-18 y (females) 123
(female puberty hormones)
Reference values are ± 2 standard deviation (SD)
Lower limits of normal are -2SD
Upper limits of normal are +2SD

5. • Normal RBC counts are 3.5 to 6.5
x1012/L (average, 5.0 x1012/L). Anemia
is associated with ↓RBC count;
thalassemia trait is associated with ↑RBC
count.
• Normal reticulocyte counts are 35 to 130
x109/L (1-2% of the RBC count). Values
<35 x109/L are reticulocytopenia and
>130 x109/L are reticulocytosis.
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RBC and Reticulocyte Counts
Methylene blue stain

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Mean Cell Volume (MCV)
(Normal values are age-dependent.)
• MCV is expressed in femtoliter (fL = 10-15 L).
• MCV <70 fL is microcytosis at any age.
Normal (Reference) Ranges
Birth 98 – 116 fL
1 mo – 10 y “70 fL + years of age” – 100 fL
> 10 y 80 – 100 fL
RBCCountRBCCountRBCCount

7. RDW (relative SD) is a measure of the variation in red
cell volume (= anisocytosis). RDW = SD ÷ MCV
Normal RDW is ≤0.14 (or ≤14%)
Relative Distribution Width (RDW)
Example: Calculate RDW for MCV = 80 fL and SD =
8 fL. RDW = SD ÷ MCV = 8 ÷ 80 = 0.1 or 10%.
RBCCountRBCCountRBCCount
anisocytosis

8. Microcytosis
• Microcytosis indicates impaired
hemoglobin synthesis (low iron or
low globin).
• Causes of Microcytosis
– Iron deficiency (↑RDW)
– Thalassemia trait (normal
RDW)
– Inflammation (blocking iron delivery to
erythrocytes)
– Ineffective protoporphyrin synthesis
(hereditary sidroblastic anemia)
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RBC should have the same size as a
small lymphocyte (arrow). The red
cells in this slide (e.g., the one pointed
by arrow head) are small (microcytosis)
Must know

9. Macrocytosis
Macrocytosis indicates impaired erythroid
replication (inadequate folate or vitamin B12).
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microcytosis macrocytosis anisocytosis
Must know

10. Neutrophil and Lymphocyte counts
Neutrophil counts should be >1.5 x109/L. Neutropenia
is an immune deficient state.
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Lymphocyte counts should be >1.5 x109/L. The majority of
peripheral lymphocytes are T cells.
Thus, lymphopenia indicates T-cell immune deficiency.
Platelet counts are 150 to 400 x109/L. Values <150 x109/L
are thrombocytopenia and >400 x109/L are thrombocytosis.
Must know

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A 12-month-old boy
1. Normal leukocyte and
platelet lineages, except
for mild neutropenia.
2. Erythroid lineage: Mild
anemia, microcytosis,
and increased RDW,
consistent with iron
deficiency anemia.

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An 18-year-old male
Microcytic anemia with normal RDW, consistent with thalassemia trait.

13. An 18-year-old female
Mild microcytic anemia (resolved)
Reticulocytosis (resolved)
Severe thrombocytopenia (resolved)

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A 7-year-old girl
Severe periodic neutropenia
Mild normocytic anemia and thrombocytosis, consistent with inflammation (infection)

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Leucopenia + neutropenia + lymphopenia
Microcytic anemia with normal RDW
Thrombocytopenia
= Pancytopenia
A 27-year-old male

16. 1. Anisocytosis
2. MCV <70 fL
3. Folate/ vitamin B12 deficiency
4. Iron deficiency
5. Thalassemia trait
6. Hemoglobin <115 g/L
7. Reticulocyte count >130 x109/L
8. Reticulocyte count <35 x109/L
9. Impaired hemoglobin synthesis
10. Impaired erythroid replication
11. Neutrophil count <1.5 x109/L
12. Lymphocyte count <1.5 x109/L
13. Adolescent males
14. Non-nucleated red cells
containing ribonucleic acid
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A. Microcytosis
B. Macrocytosis
C. Anemia
D. Neutropenia
E. Lymphopenia
F. Reticulocytopenia
G. ↑RDW
H. ↓MCV + ↑RDW
I. ↓MCV + normal RDW
J. Reticulocytes
K. ↑Hemoglobin concentration
L. Anisocytosis

17. “Must Know Pearls”
• Anemia (↓hemoglobin)
• Microcytosis = Impaired hemoglobin synthesis (iron
deficiency vs. thalassemia trait)
– Iron deficiency = ↓MCV + ↑RDW
– Thalassemia = ↓MCV + normal RDW
– RDW (= SD ÷ MCV) measures red cell size (volume) variation
(anisocytosis).
• Macrocytosis = Impaired erythroid replication (e.g., folic
acid; vitamin B12 deficiency)
• Neutropenia & lymphopenia = Immune deficiency
• Thrombocytopenia (↓platelet count)
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