Haematology Session 1 Flashcards
Give examples of haemopoietic tissue.
- Pelvis
- Sternum
- Skull
- Ribs
- Vertebra
Where does haemopoiesis occur?
Fetus: liver and spleen
Adult: bone marrow
What is a trephine biopsy?
Analysis of a liquid bone marrow sample (needle into posterior iliac crest).
What are the functions of erythropoietin and thrombopoietin?
EPO: secreted by kidney, RBC production stimulation when oxygen is low
TPO: produced by liver and kidney, regulates platelet production
What determines haemopoietic stem cell differentiation?
- Hormones
- Transcription factors
What do common myeloid progenitor differentiate into?
Cells involved in clotting.
- Platelets (Thrombopoiesis)
- Basophils (Granulopoiesis)
- Neutrophils
- Monocytes (Monocytopoiesis)
- Eosinophils
- Erythrocytes (Erythropoiesis)
What do common lymphoid progenitors differentiate into?
Lymphocytes - B and T (Lymphopoiesis)
What is extramedullary haemopoiesis?
When haemopoietic stem cells mobilise into circulating blood/colonise other tissues, eg. in thalassaemia
What are sources of haemopoietic stem cells?
- Bone marrow aspiration
- Umbilical cord stem cells (cord bank)
- G-CSF mobilised blood stem cells (leukapharesis)
What is the reticuloendothelial system?
Part of immune system that removes dead or damaged cells and identifies + destroys foreign antigens in blood and tissue via phagocytosis. Mainly spleen and liver.
What are some macrophages in blood?
- Kupffer cells (liver)
- Microglia (CNS)
- Red pulp macrophage (spleen)
- Langerhans cell (skin + mucosa)
What do RES cells do in the spleen?
Dispose of damaged and old red blood cells.
What is the function of red and white pulp in the spleen?
Red pulp: endothelial macrophages/cords, removes RBC
White pulp: similar to lymphoid follicle, where WBCs with pathogen will be destroyed.
What are the functions of the spleen (adults)?
- Phagocytosis (old cells removed by macrophages)
- Blood pooling in spleen (mobilising during bleeding)
- Extramedullary haemopoiesis (pluripotent stem cell proliferation during haematological stress)
- Immunological functions (T 25% and B 15% cells)
How does blood enter the spleen?
Splenic artery
What is splenomegaly?
Enlarged spleen
What are the causes of splenomegaly?
- Portal hypertension (cirrhotic liver - blood not passing so more drains into the splenic artery)
- Overwork
- Extramedullary haemopoiesis (as in fetal development)
- Infiltration by cells OR granulomas
How to examine the spleen?
- Should not be palpable below costal margin
- Palpate in right iliac fossa
- Feel for movement against hand during inspiration
- Feel for splenic notch
What can cause massive splenomegaly?
- Chronic myeloid leukaemia
- Myelofibrosis
What can cause moderate splenomegaly?
- Lymphoma
- Leukaemias
- Liver cirrhosis
What can cause mild splenomegaly?
- Endocarditis
- Sacroidosis
- Autoimmune disease (eg. systemic lupus erythematosus)
Why can splenomegaly result in a low blood count?
All the cells pool in the spleen and not many left in circulating blood.
Why is splenomegaly risky?
Spleen can rupture as not protected by the ribs anymore - can bleed out.
What is hyposplenism and what are the causes of it?
Lack of functioning splenic tissue.
- Splenectomy (eg. cancer)
- Sickle cell disease
- GI disease (Crohn’s, coeliac, colitis)
- Autoimmune disorders (Hashimoto’s, arthritis, lupus)
How is hyposplenism recognised on a blood film?
Howell Jolly bodies - DNA remnants (small purple dots) that would normally be removed by spleen if functioning.
What are hyposplenic patients at risk of?
Encapsulated bacteria.
- Meningococcus
- Haemophilus influenzae
- Streptococcus pneumoniae
Must get lifelong antibiotic prophylaxis + immunisation
What is the function of erythrocytes?
- Carry O2 to tissues
- Carry haemoglobin
- Remove CO2 from tissues
- Maintain haemoglobin in reduced state
What is measured in tests for RBCs?
- Red blood cell count (how many)
- Haemoglobin (effectiveness)
- Mean corpuscular volume (how large)
- Diameter (normal 8 micrometres)
What are the two configurations of haemoglobin?
Oxyhaemoglobin (relaxed) and deoxyhaemoglobin (tightly bound)
What is spherocytosis and what proteins are involved?
Haemolytic anaemia from cells being round, less deformable and fragile - removed by spleen
- Spectrin - links membrane to actin cytoskeleton
- Ankyrin - links integral membrane proteins to spectrin actin skeleton
- Band 3 - chloride/bicarbonate exchanger
- Protein 4.2 - ATP binding protein, regulates association of band 3 w/ ankyrin
How is the haem group degraded?
- Fe2+ recycled = bilirubin
- Unconjugated bilirubin transported in the blood bound to albumin
- Taken up by liver and conjugated with GLUCURONIC ACID
- Secreted in bile in duodenum
- Glucuronic acid removed by bacteria = bilirubin converted to UROBILINOGEN and then oxidised to STERCOBILIN
- Then excreted in faeces
- Some urobilinogen converted to UROBILIN when transported to kidney
- Excreted in urine
What is cytopenia?
Reduction in the number of red blood cells.
What does the suffix -penia mean?
Decrease in count of certain cells (for all but RBCs, where it’s anaemia)
What does the suffix -cytosis mean?
Increase in count of certain cells
Leucocytosis, Erythrocytosis, Monocytosis, Panmyelosis, Lymphocytosis, Thrombocytosis
What does the suffix -philia mean?
Increase in count of certain cells
Neutrophilia, Basophilia, Eosinophilia
What is the function of neutrophils?
- Phagocyte, most common white cell
- Part of innate immune system
- Invade tissues from bloodstream
- Granules in cytoplasm = digestive enzymes to kill pathogens
How is maturation of neutrophils controlled and what is recombinant G-CSF?
- Maturation controlled by G-CSF hormone (increased production, release of mature cells from bone marrow and phagocytosis)
- Recombinant G-CSF is given to patients with severe neutropenia after chemo to generate more neutrophils
What are causes of neutrophilia?
- Infection
- Cytokines (G-CSF)
- Myeloproliferative disese
- Acute haemorrhage (more cells in circulating blood)
What happens during neutrophilia?
Cells that usually stick to the side of a blood vessel (marginated) are released and so neutrophil count rises
What is neutropenia caused by?
- Reduced cell production
B12/folate deficiency, Infiltration so no room for production, Radiation (kills mature cells) Drugs (chemo, antibiotics, anti-epileptics - poison BM) Viral infection Congenital Aplastic anaemia (empty bone marrow)
- Increased removal of use
Immune destruction (autoantibodies) Sepsis - unable to generate enough to maintain circulatory numbers Splenic pooling - less in circulation
What is neutropenic sepsis?
Medical emergency - must be given antibiotics (IV) immediately
What are consequences of neutropenia?
- Severe fungal and bacterial infection
- Mucosal (mouth) ulceration
What are monocytes?
- Largest cells, migrate into tissues to become macrophages or dendritic cells
- Antigen presenting
- Phagocytosis and cellular debris breakdown
- Defend against CHRONIC BACTERIAL INFECTIONS (eg. TB)
What causes monocytosis?
- Bacterial infection
- Inflammatory conditions (eg. IBD)
- Carcinomas
- Leukaemias
What are eosinophils?
- Cells responsible for defence against multicellular parasites (helminths, worms)
- Mediate allergic responses
- Live for 8-12 days
- Phagocytose antigen-antibody complexes
What cytotoxic proteins are in the granules of eosinophils?
- Elastase
- Eosinophilic cationic protein
What are causes of eosinophilia?
Common:
- Allergies
- Drug hypersensitivity
- Churg-Strauss condition (inflammation of small blood vessels)
- Skin disease
- Parasitic infection
Rare:
- Different leukaemias (eg. eosinophilic)
- Hodgkin lymphoma
- What are basophils?
- Cells active in allergic reactions + inflammation
- Kind of look like a berry due to granules that may even cover nucleus and stain deep purple
What do basophilic granules contain?
- Histamine
- Heparin
- Hyaluronic acid
- Serotonin
What are the causes of neutrophilia?
Reactive:
- Hypersensitivity reactions (eg. drugs)
- Ulcerative colitis
- Rheumatoid arthritis
Myeloproliferative:
- eg. chronic myelogenous leukaemia
- Systemic mastocytosis
What are lymphocytes?
Cells originating in bone marrow:
- T cells - immunity; CD4+ helper cells, CD8+ , attack infected cells
- B cells - immunoglobulin-forming, attack invaders outside
- Natural killer cells - kill virally infected cells
What are the causes of lymphocytosis?
Reactive:
- Viral & bacterial infections
- Post-splenectomy as many pool in spleen
Malignant:
- T cell/NK cell leukaemia
- Lymphoma
- Chronic lymphocytic leukaemia
What are abnormal results?
Results outside normal range, however that only makes up for 95% of population so it’s possible to be outside and still normal and inside range but abnormal (if dropped from a previous reading)
Normal changes in age & sex
How are abnormal haematology results interpreted?
- Clinical context
- Previous FBCs
Explained by change/disease
What can lead to errors in pathology results?
- Specimen mix up
- Right result applied to the wrong patient
- Wrong delivery method of specimen
- Wrong bottles
- Pooling samples (when patient difficult to bleed
What is the full blood count?*
- Automated test (high output)
- Greater accuracy
- Red cells (count, Hb)
- Platelets (count, size)
- White cells (count)
What technique is used by the FBC analyser?
Spectrophotometry
- Amount of light absorbed by sample proportional to amount of compound within it
- Calibration curve to determine sample concentration
- Hypotonic solution to lyse cells
What is the other technique used by the FBC analyser?*
Flow cytometry
- Single file line of cells passes through a light beam and impedance is counted
Forward scatter = bigger cell size
What is the flow cytometry differential?*
- Forward scatter = size
- Side scatter = granules, mono/polymorphonuclear
- Myeloperoxidase (granulocyte enzyme) activity
What is packed cell volume?
The proportion of blood made up of RBCs (haematocrit)
- Used to measure polycythaemia
- Reduced by venesection/drugs
What is the haemoglobin g/L?
- Gender and age specific
- Measures haemoglobin concentration in the blood
- Clotted sample/in vitro haemolysis will reduce Hb
What is the red cell count (x10 12L)
Number of red blood cells in a given volume.
- Used to assess anaemia and erythrocytosis
- If RCC elevated, more likely to be a true polycythaemia
What is mean cell volume?
Mean RBC size as measured by the amount of light scattered as they pass single file past the laser.
- Screening cause of anaemia
What can cause a high MCV?
- Megaloblastic anaemia
- Myeloma
- Haemolytic anaemia
What can cause a low MCV?
- Iron deficiency anaemia
- Thalassaemia
- Lead poisoning
What is red cell distribution width?
- Variation in RBC size
- Anisocytosis
- Helps assess anaemia cause
What is mean cell haemoglobin?
Average measure of the amount of Hb in each RBC
- Assessment of anaemia: low in iron deficiency, higher in macrocytic anaemia
Wha is mean cell haemoglobin concentration?
Haemoglobin/Mean cell volume x Red cell count
- Reduced in hypochromia
- Increased in spherocytosis
- Not v. useful
What is the reticulocyte count?
- Size + RNA content
- High in haemolytic anaemia, recovery from BM suppression
- Reduced in BM failure
What is a blood film and when is it made?*
- Small drop of blood onto glass slide, fixed with methanol and stained to visualise under microscope
- Used when results are abnormal or where abnormal cells are suspected
What is the meaning and parameter of:
- Macro/microcytic
- Hypo/hyperchromic?
Macrocytic: MCV, large RBCs
Microcytic: MCV, small RBCs
Hypochromic: MCH, pale
Hyperchromic: MCH, more Hb
What is anisocytosis?*
Variation in RBC size
What is dimorphism?*
Two distinct populations of red cells
What is poikilocytosis?*
Abnormally shaped RBCs
What is spherocytosis?*
Spherical RBCs
What is elliptocytosis?*
Elliptical RBCs
What are echinocytes, acanthocytes and keratocytes?*
Spiculated cells
What are sickle cells?*
Crescent-shaped cells in sickle cell disease
What are target cells?*
RBCs with a dark area in middle of area of central pallor
What are schistocytes?*
Red cell fragments
What is polychromasia?*
Presence of reticulocytes
What are Howell-Jolly bodies?*
DNA/nuclear fragments present in erythrocytes.
What is basophilic stippling?*
RNA inclusions in cells
What are Peppenheimer bodies?
Iron inclusions in cells
What are Heinz bodies?*
Denatured haemoglobin
What are Haemoglobin H inclusions?*
‘Golf ball cells’
What features would be seen in iron deficiency anaemia?*
- Normal/low reticulocyte count
- Low Hb and MCV
- Pencil cells, hypochromic and microcytic
What features would be seen in spherocytosis?*
Higher reticulocyte count, higher mean cell haemoglobin concentration
What would be seen in Vit. B12 deficiency?*
- Oval macrocytes
- Howell-Jolly bodies
- Low red cell/reticulocyte count
- Low Hb
How to prevent platelets clumping in a sample?
Try citrate (green tube) sample
