Complete blood count (CBC):- Part 1 – Differential count (CBC With Platelets), Peripheral blood Smear Interpretation
Complete blood count (CBC)
- The best sample is blood in EDTA (Ethylene diamine tetraacetic acid).
- Also, prepare fresh peripheral blood smears.
- This is inexpensive, easy to perform, and rapidly done as a screening test.
- The sample can be obtained from:
- Capillary blood can be obtained from the fingertips, heel, or big toe. This is mostly done in newborns and infants.
- Venous blood can be obtained from the Anticubital vein, veins from the wrist area, or from any area where the vein is prominent.
Indications for complete blood count (CBC):
- It is a general screening test and gives tremendous information about the hematological system and other organ systems.
- It will differentiate between acute and chronic infection.
- It will diagnose and type the anemia.
- It will diagnose any type of leukemia.
- These are easy, inexpensive, and rapid to perform.
- It will find any abnormality in the count of platelets.
Precautions for CBC:
- Physical activity and stress may cause an increase in WBCs and differential values.
- Pregnancy in the final months may cause an increase in WBC count.
- Patients with splenectomy have a persistent mild increase in the WBC count.
- Drugs that may increase the WBC county are:
- Drugs that will decrease the WBC count:
- Antithyroid drugs.
Definition of CBC (Complete blood count):
- Complete blood count (CBC) includes:
- WBC count is 1 cmm in the peripheral blood.
- Differential count on the peripheral blood smears with their concentration.
- RBC count and morphology.
- Peripheral blood smears give much diagnostic information simply stained with Wright and Giemsa stain.
- The best area for appreciating the different cells in the peripheral smear is no overlapping of the cells.
- Hemoglobin gives a reddish-orange appearance to the stained cells.
Complete blood count (CBC) consists of:
- This is the differential of white blood cells (polys, lymphocytes, monocytes, basophils, and eosinophils).
- Morphology of the red blood cells.
- Hemoglobin estimation (hemoglobin which carries the oxygen).
- Platelets count.
- Peripheral blood smears and studies include:
- RBC count.
- RBC indices.
- Mean corpuscular volume (MCV).
- Mean corpuscular hemoglobin (MCH).
- Mean corpuscular hemoglobin concentration (MCHC).
- Red blood cell distribution width (RDW).
- The White cell differential count includes.
- Neutrophil count.
- Platelets count.
Advantages of CBC:
- These are inexpensive, easy, and can rapidly be done as a screening test.
- These are the basic workup of any patient with H/O fever or any other problem to advise the complete blood count.
The peripheral blood smear shows:
Red blood cells:
- The number of red blood cells and their morphology.
- There is minimal variation in size, shape, and staining of the RBCs called normocytic cells.
- A variation in the size of RBCs is called anisocytosis.
- A variation in the shape of RBCs is called poikilocytosis.
- Hypochromia is a decrease in the intensity of hemoglobin staining. It is seen when the central pallor of RBCs is >1/3 of the diameter of RBCs.
Red blood cells abnormalities seen on peripheral blood smear:
|Type of abnormality of RBCs||Characters of RBCs||Importance of abnormality of RBCs|
|Anisocytosis||The variable size of the RBCs||
|Poikilocytosis||The variable shape of the RBCs||
|Elliptocytosis||RBCs are oval in shape.||
|Acanthocytosis||Irregular spiculated surface RBCs||
|Echinocytosis||Regular spiculated surface RBCs||
|Target cell (leptocytosis)||Hypochromic RBCs with the small central zone Hb||
|Stomatocytosis||The elongated central zone of pallor in the RBCs||
|Hypochromasia||The increased central pallor of the RBCs||Low hemoglobin|
|Polychromasia||Presence of RBCs that are not fully hemoglobinized||Reticulocytosis|
White blood cells:
- The number of white blood cells, various types, and their morphology:
- WBCs are distinguished from RBCs by the presence of the nucleus.
- The automated machine counts all the nucleated cells’ RBCs as WBCs, so it needs to be corrected if nucleated RBCs are present in the blood.
- Differential white cell count gives the proportion of the different ype of white cells like neutrophils, lymphocytes, eosinophils, monocytes, and basophils.
- Visual examination of the stained slides gives the exact picture.
The differential of white blood cells:
|Type of cells||% in peripheral smear||Absolute values|
|Segmented neutrophils||50 to 70||2400 to 75000/cmm|
|Band form||2 to 6||100 to 650 /cmm|
|Lymphocytes||20 to 40||1000 to 4750 /cmm|
|Eosinophils||0 to 4||0 to 450/cmm|
|Monocytes||2 to 9||100 to 700 /cmm|
|Basophils||o to 2||0 to 200 /cmm|
- These are white blood cells containing visible granules in the cytoplasm. Are the following types:
- Neutrophils have neutral staining.
- Eosinophils show reddish eosinophilic granules.
- Basophils show bluish granules.
- Monocytes show a convoluted nucleus and are large in size.
Neutrophils or polymorphonuclear leukocytes (PMN or polys):
- 50 to 70% are mature granulocytes (segmented neutrophils) on the peripheral blood smear.
- The neutrophils’ cytoplasmic granules react with both basic and acidic stains, producing neutral or light purple granules.
- There is a characteristic dense nucleus with 2 to 5 lobes and usually 3 lobes connected by the filament.
- The nuclear chromatin is heavily clumped, coarse, or pyknotic, and stains purplish red.
- In the mature neutrophils, the Nucleochromatin is condensed into discrete lumps or lobes.
- Roughly 6% of neutrophils have one lobe called band form.
- 35% have two lobes.
- 41% have three lobes.
- 17% have four lobes.
- 2% have five lobes.
- The cytoplasm is pale with irregular outlines containing many fine -pink blue (azurophilic) or grey-blue granules.
- The life span of PMN in the peripheral blood is 6 to 10 hours.
- Band forms have less mature nuclei.
- Neutrophils are actively mobile, and many cells can gather at the site of inflammation or infection called chemotaxis.
Functions of neutrophils:
- Neutrophils are the first line of defense against tissue injury or foreign microbes.
- Segmentation of the nucleus enables these motile cells to pass through the opening of the endothelium of capillaries and target foreign substances like microorganisms.
- Neutrophils may activate the complement system.
- Induce immunoglobulin production.
- They can do phagocytosis and degrade some particles.
- They can produce an enzyme, which can destroy foreign substances ingested or phagocytosed.
- The neutrophils cytoplasm contains granules:
- Primary granules are myeloperoxidase, acid phosphatase, and other acid hydrolases.
- Secondary granules are alkaline phosphatase, lysozyme, and lactoferrin.
- Normal adult blood show 0 to 4% (1 to 5%) in the peripheral blood smear.
- Eosinophils are easily recognized by eosinophilic granules in the cytoplasm and affinity the acid eosin stain.
- In Wright’s stain, the granules are orange to reddish-orange.
- The granules are of uniform size, spherical, and evenly distributed.
- Size is slightly larger than the neutrophils and two lobes with condensed chromatin. Rarely can see three lobes.
- There is diurnal variation in the eosinophils count, with an increase at night and a decrease in the morning.
The function of eosinophils:
- These have a special role in allergic reactions.
- These are very important in parasitic defense.
- These play a role in the removal of fibrin formed during inflammation.
- In the DLC’s thin areas, these measure 15 to 18 µmand are larger than the neutrophils.
- There is abundant cytoplasm compared to the nucleus ( N: C = 2:1).
- With Wright’s stain, the cytoplasm turns dull grey-blue compared to the pink cytoplasm of the neutrophils.
- The nuclei of monocytes may be kidney-shaped, folded, indented, or occasionally lobulated.
- The nucleus shows convolutions like the brain or like a turban.
- The shape of monocytes is variable, maybe round or with blunt pseudopods.
- Four important features of the monocytes are:
- Nuclear convolutions.
- Lacy or Often delicate chromatin.
- Dull grey-blue cytoplasm.
- Blunt pseudopods.
- Digestive vacuoles may be seen in the cytoplasm.
- The half-life is 8 hours to 3 days before these cells enter the tissues and become macrophages.
- Monocytes are 2 to 9% of the normal blood leucocytes.
Functions of monocytes:
- Defensive mechanism: In different conditions like In infection, bacteria, fungi, pigments, and phagocytosed RBC may be seen in the cytoplasm.
- These cells are rarely found in the peripheral smear, which is 0 to 2%.
- Basophils have large abundant violet-blue or purple-black granules in the cytoplasm.
- These granules mostly obscure the nucleus.
- These granules measure 0.2 to 1.0 µm. These vary in number, size, and shape—these are less numerous than the eosinophil’s granules.
- These granules have an affinity for the blue or basic thiazine dyes. Basophil granules are water-soluble.
- Basophils show diurnal variation like eosinophils, increasing at night and decreasing in the morning.
Functions of basophils:
- In the tissue, they become mast cells.
- These cells have a receptor for the IgE.
- On degranulation, produce histamine.
- Lymphocytes are the second most numerous cells in the peripheral blood smears.
- Lymphocytes are 20% to 40% of adult blood cells.
- Lymphocytes are small, varying in size from 7 to 10 µm. There are intermediate and large lymphocytes.
- Wright’s stain gives blue cytoplasm varying in intensity from light to dark in different cells.
- Most lymphocytes don’t have granules.
- The nucleus size in small lymphocytes is just the size of RBCs in the same microscopic field.
- The nucleus /cytoplasm ratio is 4:1, and nuclei are round or slightly indented.
- Chromatin structure is lumpy or clumped and stains dark purple with a lighter bluish-purple area between chromatin aggregates.
- Functions of lymphocytes:
- Their main function is humoral immunity.
- B-L produces an antibody-dependent immune reaction.
- T-lymphocytes help B-lymphocytes and give rise to cell-mediated immunity.
- Platelets are produced in the bone marrow by the fragmentation of the cytoplasm of megakaryocytes.
- Each megakaryocyte gives rise to 1000 to 5000 platelets.
- The size of the platelets is 2 to 4 µm in diameter and varies in shape.
- The average number of platelets is 7 to 15/oil immersion field.
- Estimate the number of platelets in 10 oil immersion fields.
- Platelets are mostly seen in groups.
- It is necessary to count the number of platelets in the group.
- Platelets have no nucleus.
- The normal platelets are 250 x 109/L, ranging from 150 to 400 x 109/L.
- The normal life span of the platelets is 7 to 10 days. About 1/3 of the marrow output of platelets is trapped in the spleen, and it will increase in case of splenomegaly.
- Structure of the platelets:
- The platelets are the smallest structure in the peripheral blood smear, and this measure 3.0 x 4.0 µm in diameter with a mean volume of 7 to 10 fl.
- The larger platelets are >4.0 µm.
- Giant platelets measure >7.0 µm.
- Functions of platelets:
- The surface coat’s glycoproteins are important in the platelet’s reactions of adhesion and aggregation, which are the initial events in the platelet plug formation in the process of hemostasis.
- The plasma membrane phospholipids (known as platelets factor 3) are important in the conversion of coagulation factor X to Xa and prothrombin (factor II) to thrombin (factor IIa).
- The platelets contain three types of granules:
- Contains a heparin antagonist.
- Platelets-derived growth factor (PDGF).
- VWF and other factors.
- Dense granules contain:
- Adenosine diphosphate (ADP).
- Adenosine triphosphate (ATP).
- 5-hydroxytryptamine (5-HT).
- Lysosomes contain:
- Hydrolytic enzyme.
- Peroxisomes contain catalase.
Summary of the Cytochemistry of various cells found in the peripheral blood:
|Types of the cells||Peroxidase||Nonspecific esterase||Periodic Acid-Schiff (PAS)||Acid phosphatase|
|Segmented neutrophils||Positive (++)||Positive (+)||Positive (++)||Diffusely positive|
|Band neutrophils||Positive (++)||Positive (+)||Positive (+ to ++)||Diffusely positive|
|Eosinophils||Positive (++)||Negative||Negative (Cytoplasm +)||Diffusely positive|
|Basophils||Partly positive||Negative||Positive (++)||Negative|
|Monocytes||Negative to positive (- to +)||Positive (++)||Diffusely positive (+)||Positive (++)|
Focal locally positive (+)
(Acid esterase )
|Granules partly positive (+)||Often positive (+), Fine granules, and focal|
|Platelets||Negative||Positive (+)||Positive (+)||Positive (+)|
Peripheral blood normal values (CBC):
Normal Peripheral blood (CBC):
- TLC is total leucocytes count:
- 4,100 to 10900/cmm.
- DLC is differential count. Normal values:
- Neutrophils = 48 % to 77 %
- Lymphocytes = 10 % to 40 %
- eosinophils = 0.3 % to 7 %
- Monocytes = 0.6 % to 9.6 %
- Basophils = 0.3 to 1 %
- Platelets = 140,000 to 400,000 /cmm
- Male 14 to 18 g /100 ml
- Female 12 to 16 g/ 100 ml
- Pregnant female = >11 g/dL
- Old people’s values are slightly low.
|Age||Hb g/dL||Hb g/dL Male||Hb g/dL Female|
|18 to 20 weeks||11.47 ± 0.78|
|21 to 22 weeks||12.28 ± 0.89|
|23 to 25 weeks||12.40 ± 0.77|
|26 to 30 weeks||13.35 ± 1.17|
|Cord blood||13.5 to 20.5|
|1 month||10.7 to 17.1|
|2 month||9.0 to 13.0|
|4 month||10.3 to 14.1|
|9 month||11.4 to 14.0|
|one year||11.3 to 14.1|
|2 to 5 year||11.0 to 14.0|
|5 to 9 year||11.5 to 14.5|
|9 to 12 year||12.0 to 15.0||Male||Female|
|12 to 14 year||12.0 to 16.0||11.5 to 15.0|
|15 to 17 year||11.7 to 16.6||11.7 to 15.3|
|18 to 44 year||13.2 to 17.2||11.7 to 15.5|
|45 to 64 year||13.1 to 17.2||11.7 to 16.0|
|65 to 74 year||12.6 to 17.4||11.7 to 16.1|
- For conversion into SI units x 10 = g/L
- Critical value = <5 g/dL or >20 g/dL
ESR (Erythrocytes sedimentation rate):
- Male Older than 50 years = 0 to 15 mm/ hour
- Female = 0 to 25 mm /hour
- Child = up to 10 mm/hour
- Newborn = 0 to 2 mm/hour
Normal Platelet count:
- Adult = 140,000 to 400,000/cmm
- Children = 150,000 to 450, 000/cmm
- Platelets are assessed by the smear or by a Haematology analyzer.
Neutrophils increased in:
- Myocardial infarction.
- Metabolic diseases.
Neutrophil Decreased in:
- In radiation therapy or chemotherapy.
- Folic acid or B12 deficiency.
- Hepatic diseases.
- collagen vascular diseases.
Eosinophils increased in:
- Parasitic infestation.
- Skin disorders.
- Neoplastic diseases like Hodgkin’s lymphoma.
- Collagen vascular diseases.
Eosinophil Decreased in:
- Cushing’s syndrome.
Lymphocytes increased in:
- Chronic infections.
- Lymphocytic leukemia.
- In immune diseases, e.g, Ulcerative colitis.
Lymphocyte Decreased in:
- Chronic debilitating illness.
Monocytes increased in:
- Collagen vascular diseases.
- Monocytic leukemia.
Basophils Increased in:
- Chronic myelocytic leukemia.
- Polycythemia vera.
- Hodgkin’s disease.
- In some anemias.
Basophil Decreased in:
- Note: please see more information on peripheral and RBC smear.