Haematology: RBC Flashcards
What are the functions of a capillary?
- Allows oxygen, glucose, fats and protein to reach tissues
- Allow carbon dioxide, urea and creatinine to be removed
- Allow clotting factors and WBC to access areas when damaged
- Allow messages in the form of hormones
What is blood?
The substance that ensures tissues all over the body receive nutrition, oxygenation, immunity, communication and waste management
What is the pH of blood?
-7.4
What is haematology?
The study of blood cells
What is biochemistry?
The study of chemical and biological substances within the blood (plasma or serum)
What can we measure with haematology?
- PCV/Haematocrit
- Haemoglobin
- RBC number and morphology
- WBCC
- WBC types and morphology
- Platelet count
What can we measure with biochemistry?
- Nutrients
- Wastes
- Enzymes
- Hormones
- Clotting
How should we take blood samples and why?
- Should use the widest gauge (green) to minimise haemolysis (damaging of cells)
- Should use the smallest appropriate syringe to minimise clotting
What is plasma?
- The liquid, cell-free part of blood that has been treated with anti-coagulants
How should we add blood in the blood tube and why?
- Remove needle from syringe before adding blood, as it can damage the cells
- Add blood to tube, invert 5-10x to mix with anticoagulant or to encourage clotting in serum tubes
What is serum?
- The liquid part of blood after coagulation; therefore devoid of clotting factors as fibrinogen
- Has higher protein than plasma
- Ultimately, serum = plasma - fibrinogen/clotting factors
What is the order of adding blood to blood tubes to prevent cross-contamination?
-Citrate
- Serum
- Gel
- Heparin
- EDTA
- Fluoride-oxalate
What is a white blood tube?
- No additive
- Used for serum for biochemistry
- Encourages clotting
What is a brown blood tube?
- Gel additive
- Used for serum for biochemistry
- Encourages clotting and gel separates clot from serum
What is a orange blood tube?
- Lithium heparin anticoagulant additive
- Used for biochemistry
- Heparin inhibits clotting pathway
What is a red/pink blood tube?
- Potassium EDTA anticoagulant additive
- Used for haematology
- EDTA irreversibly binds calcium and preserves cell morphology
What is a lavender blood tube?
- Sodium citrate anticoagulant additive
- Used for clotting tests
- Citrate reversibly binds calcium
What is a yellow blood tube?
- Fluoride oxalate anticoagulant additive
- Used for glucose and lactate
- Fluoride prevents cells using glucose or producing lactate and oxalate irreversibly binds calcium
How should anti-coagulant samples be processed?
- Heparin, fluoride-oxalate or citrate: Use whole blood for in house analysers or if sending to external lab, it needs to be centrifuged and then plasma needs to be taken out using a pipette and dispensed into a plasma tube
- EDTA: Don’t centrifuge, as cells are needed
How should serum samples be processed?
- Add blood to tube and invert to encourage clotting
- Leave to clot for 10-30 min at room temperature
- Centrifuge
- Plain: remove serum or RBC in clot start to lyse and release contents which affect the serum
- Serum: Don’t remove serum
How should blood samples be stored?
- EDTA haematology: use immediately or store in fridge for 12 hours
- Plasma and separated serum: use within 4 hours or store in fridge
How are blood cells formed?
- Produced in the bone marrow
- Stem cells produce all types of blood cells
What is haematopoiesis?
- Formation of blood cells
What are lymphocytes?
- Cells of the lymphoid lineage
What are myeloid cells?
- Cells of the myeloid lineage (erythrocytes, platelets, granulocytes and monocytes)
What are erythropoiesis?
- Formation of RBCs
What is lymphopoiesis?
- Formation of lymphocytes
How are WBCs produced?
- Activated WBCs release cytokines that stimulate the production of more WBCs
How are RBCs produced?
- Decreased oxygen levels trigger the release of erythropoietin from the kidneys, stimulating RBC production
How are platelets produced?
- Thrombopoietin released form the kidneys and liver stimulate platelet production
What sample medium do we need to run a haematology test?
- EDTA (red/pink blood tube)
- Blood smear
What are the common components of a haematology analyser?
- RBCC
- PCV/Haematocrit
- MCV
- MCHC
- Reticulocyte count
- Platelet count (PLT)
- Plateletcrit (PCT)
- WBCC
- Differential % and absolute count of neutrophil, lymphocyte, eosinophil, basophil and monocytes
How does a haematology analyser work?
- Individual cells are passed through the analyser
- Analyser detects their size and granularity and this allows it to decide what type of cell is is and the number of these in the volume of blood
What is the RBC morphology?
- Biconcave disk
- Appears like a doughnut on microscopy
What is erythropoiesis?
- Erythrocyte maturation
What do very young erythrocytes look like?
- Large cells
- Have a nucleus
- No haemoglobin
What do young erythrocytes look like?
- Small
- Haemoglobin
- Nucleus shrinks
- Nuclear remnant extruded
What do reticulocyte look like?
- No nucleus
- Fine RNA threads in cytoplasm
- These enter blood circulation at this stage
What do mature erythrocytes look like?
- Small cells
- No nucleus
- Much haemoglobin
What is the lifespan of a erythrocyte?
- 110 days in a dog
- 70 days in a cat
How long do reticulocytes take to mature in the blood?
- 24 hours
How are damaged, old or diseased RBCs removed from the blood?
- Removed by the spleen or liver
- Haem of haemoglobin broken into bilirubin (yellow colour) and iron
- Bilirubin is removed by bile ducts into the gall bladder and then the duodenum
- Iron of haemoglobin is recycled into blood
What does HCT mean?
- Packed cell volume (PCV)
What does MCV mean?
- Mean corpuscular volume
What does MCHC mean?
- Mean corpuscular haemoglobin concentration
What does PCV tell us about the assessment of erythrocytes?
- Estimate RBC count
What does blood smears tell us about the assessment of erythrocytes?
- Morphology
What is PCV?
- The % of blood volume, made up of RBCs
How is a PCV carried out?
- Fill a capillary tube with blood, centrifuge to make RBC settle at the bottom
- Analysers measure haemocrit
- By measuring the % volume of red blood cells, can estimate the number in circulation
What are erythrocytes assessed on from a bloods smear?
- Size (MCV)
- Variation in size between cells (RDW)
- Shape
- Inclusions
- Agglutination
What should a normal blood smear look like?
- Most cells should be mature erythrocytes
- Some reticulocytes
What happens if there is a low RBCC in circulation?
- Tissues don’t receive enough O2 and CO2, so become hypoxic and this can cause anaemia
What happens if there is a high RBCC in circulation?
- RBCs cells are quire large, so increased numbers can cause blood to become more viscous, which limits blood flow
What is anaemia?
- Reduction in number of circulation erythrocytes
What are the clinical signs for acute anaemia?
- Profound lethargy
- Weakness
- Tachycardia
- Tachpnoea
What are the clinical signs for chronic anaemia?
- Appear clinically normal, as the body learns to compensate for the low oxygen levels, but low PCVs
What is the normal PCV range in a dog?
- 39-55%
What is the normal PCV range in a cat?
- 24-45%
What are the different types of anaemia?
- Regenerative
-Non-regenerative
What is regenerative anaemia and what does it cause?
- Increased RBC loss
- Causes haemorrhage and haemolysis
- Reticulocytes present in blood, showing bone marrow trying to restore normal RBC numbers
What is non-regenerative anaemia?
- Decreased RBC production
- Caused by a disorder of bone marrow and/or disorder outside bone marrow
- None or very few reticulocytes present in blood
What are the causes of anaemia?
- Haemorrhages
- Haemolysis
- Lack of RBCs due to bone marrow disorder
- Lack of RBCs due to problem outside bone marrow
What are some disorder with the bone marrow?
- Bone marrow suppression caused
by chemotherapy and hyper-oestrogenism - Bone marrow disorder caused by lymphoma or FelV/FIV/parvo
What are some problems outside the bone marrow?
- Lack of erythropoietin which can cause renal disease and lack of iron
What is haemolysis?
- The premature destruction of RBCs
- Usually RBCs phagocytosed in liver and spleen
-Occasionally RBCs burst in circulation due to antibodies - Can also be caused by poor venepuncture technique (suction, needle size and syringe size)
How is anaemia diagnosed?
- Pale MM and low PCV = No increase reticulocytes and a increase in reticulocytes
- If there are reticulocytes, may be RBC loss or destruction, which can cause bleeding and jaundice
- if no reticulocytes, may be bone marrow disorder or lack of erythropoietin, which can cause decrease in WBC and platelets, PUPD, lethargy and anorexia
How is a haemorrhage diagnosed?
- Cells vary in size, an increase in MCV= more reticulocytes
- Cells vary in colour, decrease in MCHC= more reticulocytes
- May be inclusions
- May be obvious blood loss
How is haemolysis diagnosed?
- Cells vary in size, an increase in MCV= more reticulocytes
- Cells vary in colour, decrease in MCHC= more reticulocytes
- May be inclusions
- Can cause jaundice
How can anaemia be investigated via a blood sample?
- PCV (degree of anaemia)
- Blood smear (Presence of reticulocytes)
- Analyser (confirmation of RBCC)
What is erythrocytosis?
- High concentration of RBCs
What are the clinical signs of erythrocytosis?
- Red MMs
- Lethargy
- Depressed
- Neurological signs
What are the different types of erythrocytosis?
- Relative (water losses/dehydration or splenic contraction)
- Absolute (primary and secondary types)
What causes relative erythrocytosis?
- Dehydration artificially raises PCV and plasma proteins are more concentrated
- Stress/excitement due to splenic contraction
What causes absolute erythrocytosis?
- Primary: Neoplasia in kidney or bone marrow and abnormal cell production
- Secondary: Hypoxaemia due to cardiac, respiratory or kidney disease, and excess hormones
How is erythrocytosis diagnosed?
- Both relative and absolute present
- Increased PCV (important to measure TP in addition to PCV with refractometer)
What does a low PCV and a normal TP mean?
- Anaemia
What does a high PCV and a normal TP mean?
- Erythrocytosis
What does a high PCV and a high TP mean?
- Dehydrated
What does a low PCV and a low TP mean?
- Over dehydrated
