Intro to Haematology Flashcards
What are the 4 main subdivisions of haematology in clinical practice?
- Coagulation
- Malignant
- Non-malignant
- Transfusion
What is haemopoiesis?
The physiological developmental process that gives rise to the cellular components of blood. A single multipotent haemopoietic stem cell can divide and differentiate to form different cell lineages that will populate the blood .
A stem cell can undergo different types of self-renewal. Explain these;
a) symmetric
b) asymmetric
c) symmetric differentiative/consuming
a) giving rise to two identical daughter stem cells
b) give rise to one stem cell and a more differentiated cell
c) generate two differentiated daughters
What are the first 2 sites of intraembryonic haematopoiesis?
1) Yolk sac
2) AGM (Aorto-Gonado-Mesonephros); a region of embryonic mesoderm
After the yolk sac and AGM, where does haemopoiesis then progress to?
- Hematopoietic stem cells migrate to the foetal liver,
* Then spleen and bone marrow (week 20)
What is extramedullary hematopoiesis?
Haematopoiesis occurring outside of the medulla of the bone (bone marrow). It can be physiologic or pathologic.
Physiologic EMH occurs during embryonic and foetal development; during this time the main site of foetal hematopoiesis are liver and the spleen.
What is pancytopenia?
A condition where a person has low counts for all 3 types of blood cells; RBCs, WBCs and platelets. This is usually due to a problem with the bone marrow.
Lifespan of erythrocytes?
120 days in blood
What is polycythaemia?
Raised levels of RBCs
What is relative polycythaemia?
An apparent rise of the erythrocyte level in the blood; however, the underlying cause is reduced blood plasma (hypovolemia, cf. dehydration). Relative polycythemia is often caused by loss of body fluids, such as through burns, dehydration, and stress.
What are granulocytes?
What 3 types of cells make up granulocytes?
A type of immune cell that has granules with enzymes that are released during infections, allergic reactions, and asthma. A granulocyte is a type of white blood cell.
1) Neutrophils
2) Eosinophils
3) Basophils
Which is the main granulocyte?
Neutrophils
What is the most common white cell in adult blood?
Neutrophils
What is neutrophilia? Caused by?
increased numbers of neutrophils
E.g. bacterial infection, inflammation
What is neutropenia? Caused by?
decreased numbers of neutrophils
E.g. side effect of drug (chemo)
What is eosinophilia? Caused by?
increased numbers of eosinophils
E.g. parasitic infection, allergies
What is basophilia?
What is it a hallmark of?
increased numbers of basophils
this is a hallmark of Chronic Myeloid Leukaemia
What are monocytes?
After they migrate to the tissue, what are they called?
Monocytes are the largest type of leukocyte.
Migrate to tissues & are then identified as “macrophages” or “histiocytes”
What are resident macrophages of the
a) liver
b) skin
known as?
a) Kupffer cells
b) Langerhans cells
What is monocytosis? What disease can it be seen in?
increased numbers of monocytes e.g. TB
What is lymphocytosis?
Increased numbers of lymphocytes
E.g. atypical lymphocytes of glandular fever (infectious mononucleosis)
E.g. Chronic lymphocytic leukaemia
What is lymphopenia?
decreased numbers of lymphocytes e.g. post bone marrow transplant
What are the three major types of lymphocyte?
1) T cells
2) B cells
3) NK cells
What is plasmacytosis?
Increased numbers of plasma cells e.g. infection, myeloma
What are platelets? What are they derived from? Function?
- Are not cells but small fragments of cells; derived from bone marrow megakaryocytes
- Together with soluble plasma clotting factors and endothelial cells form part of the blood clotting system
- Aggregate to plug holes in damaged blood vessels
What is a ‘reference range’?
- The set of values for a given test that incorporates 95% of the normal population (arbitrary convention)
- Determined by collecting data from vast numbers of laboratory tests
i.e. 95% healthy results fall within the reference range
What is a ‘false positive’?
healthy people with result outside normal range
What is a ‘false negative’?
diseased people with result within normal range
What is intra-individual variation in test results?
Variability within individuals
E.g. diurnal variation of cortisol levels
What is inter-individual variation in test results?
Differences that are observed between people
e.g. platelet count
Things to consider when establishing a reference range:
- Reference population should be relevant to the test population i.e. age, sex, ethnicity, etc
- Consider if separate ranges are required for; adults versus children, men versus women, pregnant vs non-pregnant, etc
- Determine the expected range of inter-individual variation
What is sensitivity?
Defined as the proportion of abnormal results correctly classified by the test. Sensitivity = TP / (TP+FN) i.e. TP / all that have the disease
o Think of this like a sensitive person – pick up on even minor irregularities
o Expresses the ability to DETECT a true abnormality
What is specificity?
Defined as the proportion of normal results correctly classified by the test. Specificity = TN / (TN+FP).
o Expresses the ability to EXCLUDE an abnormal result in a healthy person
Potential causes of an abnormal lymphocyte count:
post-splenectomy mild lymphocytosis
3 months post-bone marrow transplant lymphopenia
Neutrophilia in pregnancy or with steroid use
Polycythaemia for athlete training in altitude conditions
Thrombocytopenia in liver disease with portal hypertension and large spleen
Describe the RBCs in ‘microcytic hypochromic’ anaemia?
Small and pale
Most common cause of microcytic anaemia?
iron deficiency
Other causes of microcytic anaemia?
Iron deficiency Thalassaemia Anaemia of chronic disease (some) Lead poisoning Sideroblastic anaemia (some cases)
What is ‘normocytic normochromic’ anaemia?
Forms of anaemia in which the average size and haemoglobin content of the red blood cells are within normal limits
What is ‘normocytic normochromic’ anaemia seen in?
Many haemolytic anaemias
Anaemia of chronic disease (some cases)
After acute blood loss
Renal disease
Mixed deficiencies
Bone marrow failure (e.g. post-chemotherapy, infitration by carcinoma etc)
What is the most common cause of macrocytic/megaloblastic anaemia?
B12 or folate deficiency
What is non-megaloblastic anaemia? What are the main causes?
Non-megaloblastic macrocytic anaemias are those in which no impairment of DNA synthesis occurs.
alcohol, liver disease, myelodysplasia, aplastic anaemia etc
What information does a FBC give?
- Haemoglobin concentration (Hb)
- Red cell parameters
- MCV (mean cell volume)
- MCH (mean cell Hb)
- Reticulocyte Count
- White Cell Count (WCC)
- Platelet Count (Plt)
What is a coagulation screen?
Tests measure the time taken for a clot to form when plasma is mixed with specified reagents.
What 3 parts of the coagulation cascade can be assayed in a coagulation screen?
o Prothrombin Time
o Activated Partial Thromboplastin Time
o Thrombin Time
What is a bone marrow trephine biopsy?
When a tiny core of the bone marrow tissue is removed. This is then processed and sliced very thinly. It can be looked at under the microscope to see how the cells lie while they are actually in the bone marrow.
What is the anticoagulant of choice for hematological testing?
EDTA - allows the best preservation of cellular components and morphology of blood cells.
What is important to remember regarding EDTA in a FBC?
Samples should get to the lab promptly since EDTA artefact can affect the results.
Appearance of RBCs in iron deficiency anaemia?
- Small, pale red cells (low MCV and MCH),
- Variable size & shape – NB long thin “pencil” cells
Appearance of RBCs in B12 deficiency anaemia?
Hypersegmented neutrophils & oval macrocytes
