Haematology is the study of blood, including:
Haemopoiesis
Formed elements of blood
Haemoglobin
Coagulation
Blood transfusion / cross matching
Blood and bone marrow are intensively studied in haematology.
The average adult has approximately 5 litres of blood.
Blood is found in:
Circulatory system
Sinusoids
Blood supports the function of body tissues.
Blood is a tissue composed of:
Formed elements:
White blood cells (leucocytes)
Red blood cells (erythrocytes)
Platelets (thrombocytes)
Liquid component: Plasma
The production of the formed elements of blood (WBCs, RBCs, and platelets).
Erythropoiesis: Production of RBCs.
Thrombopoiesis: Production of platelets.
Granulopoiesis: Production of granulocytes.
Lymphopoiesis: Production of lymphocytes.
Monocytopoiesis: Production of monocytes.
All cell lines are derived from a single precursor cell.
A stem cell differentiates into mature cells under the influence of growth factors.
Sites of Haemopoiesis:
Foetus: Yolk sac, liver, spleen, bone marrow, lymph nodes.
Adult: Bone marrow.
Multipotential hematopoietic stem cell (Hemocytoblast) differentiates into:
Common myeloid progenitor:
Erythrocyte
Mast cell
Myeloblast:
Basophil
Neutrophil
Eosinophil
Monocyte → Macrophage
Megakaryocyte → Thrombocytes
Common lymphoid progenitor:
Small lymphocyte:
T lymphocyte
B lymphocyte → Plasma cell
Natural killer cell (Large granular lymphocyte)
Red Blood Cell (RBC):
Most numerous type of cell in blood.
Anuclear.
Biconcave disc shape, with an "Area of central pallor".
Diameter: 7.2 - 8.0 µm.
Lifespan: 120 +/- 20 days.
Contains haemoglobin, which transports oxygen and gives RBCs a red colour.
Shape allows rapid diffusion of gases and flexibility.
Shape maintenance depends on energy and membrane structure (lipid protein carbohydrate).
Platelets:
Second most numerous type of cell in blood.
Discoid shape.
Anuclear.
Diameter: 3 µm.
Small cytoplasmic fragments derived from megakaryocytes.
Primary role is the prevention of blood loss.
White Blood Cells:
Granulocytes (with cytoplasmic granules):
Neutrophils
Eosinophils
Basophils
Agranulocytes (no cytoplasmic granules):
Lymphocytes
Monocytes
Neutrophils:
Most common type of WBC.
Diameter: 9 - 15 µm.
Multi-lobed nucleus.
Small granules in cytoplasm.
Polymorphonuclear cells.
Spend 8 - 10 hours in circulation.
Involved in bacterial and fungal infections.
Eosinophils:
Bi-lobed nucleus.
Diameter: 9 - 15 µm.
Large, strongly staining (orange/red) cytoplasm granules.
Circulate for 4-5 hours.
Defence against parasitic infections.
Dampen allergic responses.
Basophils:
Least numerous circulating WBCs.
Diameter: 10 - 16 µm.
2 - 4 lobes in nucleus.
Large cytoplasmic granules (dark staining).
Involved in hypersensitivity and inflammatory reactions.
Lymphocytes:
Second most common WBC in peripheral blood.
Diameter: 8 - 10 µm (Small), 12 - 16 µm (Large).
Large round nucleus/less cytoplasm.
Variable lifespan: few days - years.
T-lymphocytes: cell-mediated immunity.
B-lymphocytes: humoral immunity.
Monocytes:
Largest WBC (14 - 20 µm diameter).
Kidney-shaped nucleus.
Circulate for ~ 10 hours.
Exit into tissues and become macrophages.
Removal of aged RBCs and other debris.
Antigen processing and presentation to T lymphocytes.
Abnormal morphology.
Abnormal cell number (abnormal cell counts).
Morphology refers to the “appearance” of a cell.
Abnormal cell morphology indicates a change in cell structure/function.
Changes to the size and shape of RBCs can indicate:
Abnormal erythropoiesis.
Inadequate Hb formation.
Direct damage after leaving bone marrow (BM).
Compensatory erythropoiesis.
Change in size of RBC: Anisocytosis.
Change in shape of RBC: Poikilocytosis.
Decreased size: Microcytosis.
Increased size: Macrocytosis.
Elliptocytes:
Thin elongated cigar shaped cells.
Change to membrane structure.
Found in various types of anaemia.
Ovalocytes:
Oval shaped rather than thin or round.
Less pronounced defects.
Found in some types of anaemia.
Codocytes (target cells):
Loss of biconcave shape.
Increased surface area:volume ratio.
Spherocytes:
Loss of biconcave shape - sphere.
Decreased surface area:volume ratio.
Found in many anaemias.
Schistocytes (RBC fragments):
Irregularly contracted fragments.
Variable appearance.
Found in conditions with trauma to RBCs (e.g., burns).
Drepanocytes (sickle cells):
Elongated, crescent shaped.
Sickle cell anaemia.
Abnormal haemoglobin (HbS).
Acanthocytes (burr cells):
Multiple irregular thorny projections.
Changes in phospholipid metabolism.
Found in liver disease.
Dacrocytes (teardrop cells):
Teardrop shape.
Stretched out of shape - excessive time (spleen).
Found in many conditions.
Stomatocytes:
Oval or rectangular area of central pallor.
“Cup”-shaped.
Found in liver disease.
Echinocytes:
Short, evenly spaced pointed projections.
Acute blood loss, burns, uraemia - kidney failure.
Reticulocyte:
Immature RBC (newly released to circulation).
Contain some RNA but are not nucleated.
May show polychromasia.
Small percentage of reticulocytes in circulation in normal individuals.
Nucleated RBC (nRBC):
Developing RBC.
Released from bone marrow prematurely.
Found in severe anaemias, especially early childhood anaemia.
Hypochromasia:
“Hypo”- less, “chrom”- colour.
Cells stain paler in colour.
Enlarged area of central pallor.
Decreased Hb content - anaemia.
Polychromasia:
“Poly” - many, “chrom” - colour.
Variable colour [Blue/grey - orange/red].
Increased number of immature RBCs.
Rouleaux:
Stacking of cells due to high protein concentration.
Agglutination:
Clumping of cells due to antibodies.
A number of inclusions may be found in RBCs.
Help identify abnormalities/disease.
Examples: Malaria, Howell-Jolly Body, Basophilic Stippling.
Many changes to WBC morphology.
Help identify abnormalities/disease.
Toxic granulation – increased size of granules.
Left shift neutrophils - immature.
Right shift neutrophils - older.
A healthy adult has ~ 5 litres of blood.
Cell numbers remain relatively constant in health.
Changes occur in disease: e.g., ↑ of WBC in leukaemia (a cancer of blood forming cells), e.g., anaemia ↓ in RBC.
The number of cells in circulation is given as a number per unit of volume.
Outside these ranges indicate disease.
Suffix used to denote the type of change:
Increased numbers: -cytosis or -philia.
Decreased numbers: -aenia.
Cells | Units | Reference Range |
---|---|---|
WBC’s | (x 109$$10^9$$/L) | 4.0 - 11.0 x 109$$10^9$$/L |
RBC’s | (x 1012$$10^{12}$$/L) | 4.50 - 6.50 x 1012$$10^{12}$$/L (m) |
3.80 - 5.80 x 1012$$10^{12}$$/L (f) | ||
Platelets | (x 109$$10^9$$/L) | 150 - 400 x 109$$10^9$$/L |
Blood Cell | Increased | Decreased |
---|---|---|
RBC | Erythrocytosis | Anaemia |
WBC | Leucocytosis | Leucopaenia |
Neutrophil | Neutrophilia | Neutropaenia |
Lymphocyte | Lymphocytosis | Lymphopaenia |
Monocyte | Monocytosis | Monocytopaenia |
Eosinophil | Eosinophilia | N/A |
Basophil | Basophilia | N/A |
Platelets | Thrombocytosis | Thrombocytopaenia |
All formed | Pancytopaenia |
Cell counts are performed to:
Determine if disease is present.
Monitor the course of disease (treatment).
The count should be accurate and precise.
Counts are obtained by either of two methods:
Manual or.
Automated.
RCC (number of RBCs per litre of blood): Red Cell Count
WCC (number of all WBCs per litre of blood): White Cell Count
All cells in a small volume are counted.
The count is extrapolated to give # per L of blood.
Cells are counted using a microscope.
Blood is diluted (high numbers in whole blood).
Counting chamber (haemocytometer).
Calibration - international specifications.
NOTE: – Different dilutions and diluents: WHY??
Manual cell counts.
Blood cells.
Others:
Bacterial cells in suspension.
WBC’s in CSF.
Improved Neubauer Counting Chamber.
1 mm x 1 mm (i.e. 1 mm2$$mm^2$$)
Each square = 1 x 1 mm.
Each square = 1 mm2$$mm^2$$.
i.e. 4 x 1 mm2$$mm^2$$ = 4 mm2$$mm^2$$
Number of cells per litre = mean count x D x DF x 106$$10^6$$ / A (mm2$$mm^2$$)
D = Depth factor - the amount by which the count is multiplied to give the number of cells there would be in 1mm depth. For a 0.1 mm deep chamber (such as the Improved Neubauer Counting Chamber) the Depth Factor would be 10.
DF = Dilution Factor (by what factor was the sample diluted)
106$$10^6$$ = Conversion Factor (from mm3$$mm^3$$ to litres)
A = Area of chamber (counted in mm2$$mm^2$$)
Technical error:
Dilution - small volume of blood is used.
Sampling - blood evenly mixed, adequate sample transfer to chamber.
Counting - recognise cells correctly.
Statistical error:
Only a small sub-population of cells are being counted from the total number of cells.
Widely used in laboratories.
Full blood count provided in < than 1 minute.
Faster, more cells counted, accuracy, precision.
Two main principles of cell counting used:
Electrical impedance.
Light scatter.
RBC’s - 1 in 50,000 dilution.
WBC’s - 1 in 500 (RBC’s lysed).
Coincidence error for Impedence counters only – Duplicate cells counted as one cell.
Background count.
Distribution of cells in diluent.
Dilution technique.
Contamination.
Immersion of sample.
The result from a cell count (manual or automated) will be interpreted the same way.
Compare result to: reference range.
Classify as: low, normal or high.
Total number of all WBCs = WCC = 15.4 x 109$$10^9$$/L (Reference range = 4.0 - 11.0 x 109$$10^9$$/L)
Result is high i.e. above reference range.
“Leucocytosis”.
Same approach for all parameters.
“The Diff”.
Count the proportion of the 5 different WBC’s.
Manual count = Count 100 consecutive WBC’s.
Relative numbers (%) = how many of that type of WBC (N, L, M, E, or B) per 100 WBCs.
Then convert the Relative count (%) to Absolute numbers (x 109$$10^9$$/L).
Absolute count = % each type of cell x total WCC / 100
Example 1: Normal
Example 2: Leukocytosis with a marked Lymphocytosis
In addition to abnormal cell morphology and WCC/Diff, other information can assist in diagnosis:
RCC, platelet count, ESR, PCV, Hb, RBC Indices: MCV, MCH, MCHC
More on these, Cross-matching, Coagulation if you study Haematology in 2nd year.
Haematology Lecture Notes
Cells | Units | Reference Range |
---|---|---|
WBC’s | (x 109/L) | 4.0 - 11.0 x 109/L |
RBC’s | (x 1012/L) | 4.50 - 6.50 x 1012/L (m) |
3.80 - 5.80 x 1012/L (f) | ||
Platelets | (x 109/L) | 150 - 400 x 109/L |
Blood Cell | Increased | Decreased |
---|---|---|
RBC | Erythrocytosis | Anaemia |
WBC | Leucocytosis | Leucopaenia |
Neutrophil | Neutrophilia | Neutropaenia |
Lymphocyte | Lymphocytosis | Lymphopaenia |
Monocyte | Monocytosis | Monocytopaenia |
Eosinophil | Eosinophilia | N/A |
Basophil | Basophilia | N/A |
Platelets | Thrombocytosis | Thrombocytopaenia |
All formed | Pancytopaenia |
NOTE: – Different dilutions and diluents: WHY??