Red Blood Cell Parameters Flashcards
What is polycythaemia?
The presence of too many red blood cells
What elements of the FBC are increased in polycythaemia relative to comparision of normal subjects of the same age and gender?
RBC, Hb and Hct
What is pseudopolycythaemia
When the blood plasma volume is reduced to it appears as though there is more red cells in a sample
What are the four causes of polycytheamia?
Blood doping / transfusion
Appropriately increase erythropoietin
Inappropriately increased erythropoietin synthesis / use
In what situations might you expect to find a raised erythropoietin level?
Eg as a result of hypoxia due to high altitudes
What are two causes of inappropriate erythropoietin use / synthesis?
Blood doping for a competitive advantage
Kidney tumour secreting too much eryrthropoietin
What is the name of the condition given to polycythaemia which arises from inappropriately increased erythropoietin?
Polycythaemia vera
Why is polycythaemia a myeloproliferative disorder?
It refers to the proliferation of any of the myeloid cell lineages - in this case it is increased erythropoiesis
How can polycythaemia be treated?
Drugs given to reduce the bone marrow production of cells
Why is polycytheamia treated with a venesection?
Polycythaemia can lead to thick blood, which is known as hyperviscosity which leads to vascular obstruction and blood vessel thrombosis - therefore removal of some blood can help reduce the viscosity
Why might a patient with an abdominal mass have raised Hb concentration?
Kidney tumour - inappropriate erythropoietin secretion
Why might a patient with breathlessness?
hypoxia leading to appropriately increased erythropoietin
Why might a young healthy athlete have raised Hb concentration?
Blood doping or inapporpriate erythropoietin use
What is anaemia?
Anaemia is a reduction in the amount of haemoglobin in a given volume of blood below what would be expected in comparison with a healthy subject of the same age and gender
How is MCV Calculated?
Hct / RBC
Why might athletes participate in blood doping?
To increase their blood binding capacity
What is central cyanosis?
Blue discoloring seen on lips and tongue due to low oxygen levels / hypoxia
What fraction of the red blood cell should the central pallor take up?
Less than 50% of the cell
What is the difference between MHC and MCHC?
MHC is the absolute amount of hemoglobin in an individual red cell
MCHC is the average concentration of Hb in a red cell which also relates to the shape of the cell
If a patient has a low MCV but a high RBC, what condition are they likely to have?
Thalassemia trait
If MCV, MHC, MCHC and RBC are all low, what condition is the patient likely to have?
Iron deficiency anaemia
Why is it important to distinguish between those with iron deficiency and thalassemia?
So that you can prescribe iron to those lacking iron and therefore prevent them having too much iron
Describe safety considerations which should be made before taking blood for analysis
- Clean skin with an alcohol swab before puncture
- Protect the wound with a plaster
- Wear disposable gloves and wash you hand immediately if any contact with the blood is made
4.
Describe how to collect a capillary blood sample
- Explain the test to the donor and gain consent
- Put gloves on and clean the sonors hands with alcohol gel - clean the puncture site with a swab
- Puncture using a disposable lancet
- To draw blood place pressure firmly on the area of the puncture, and a drop of blood should come out
Describe how a Red Cell Count is performed
- Aspirate a 5 microL sample of the donors blood from a piece of parafilm and place into a pre made Eppendorf and mix gently
- Place slide on top of haemocytometer
- Then, pipette a small amount of blood onto the haemocytometer so that capillary action pulls the fluid under the slide
- Place under the light microscope and count the number of RBCs in an equal number of non-adjacent small squares (totalling 80)
- Extrapolate by 10^12 for cells / L vaulue
Describe how to measure haemoglobin from a patients blood sample
- Fill a haemocue cuvette with blood from the donor - use the second drop obtained
- wipe the donors blood clean
- Place the cuvette into a Haemocue device and analyse
Describe how to obtain a Haematocrit value
- Elicit a drop of blood from the donors finger and wipe away
- Next, elicit a large drop of blood on the end of the participants finger and lower the capillary tube into it vertically.
- As the capillary tub fills, slowly lower the top towards a more horizontal orientation. Allow it to fill to about 1 cm from the other end.
- Centrifuge the sample
- place into Haematocrit reader
How does a haematocrit reader work?
As the tube is of uniform diameter, the ratio of the length of the fluid column to the total length of the cells and the plasma is the haematocrit - To read, lay the tube in the reader groove and slide down so the putty/blood border is on the horizontal black line. Now move the slider until the upper black line intersects the top of the plasma. Then raise/lower the white line to intersect the red cells/plasma border and read off the scale on the right. Remember to divide by 100 to report in the appropriate units.
What is MCV?
Mean Cell Volume - average volume of each Red Cell
What is Mean Cell Haemoglobin?
The average mass of Hb in each cell
What is MCHC?
Mean Cell Haemoglobin Concentration - the average concentration of Hb in each RBC, takes into account the shape of the RBC as well
what is the formula to calculate MCV?
MCV = Hct / RBC
What is the formula the calculate MCH?
MCH = Hb/RBC
What is the formula to calculate MCHC?
MCHC = Hb/Hct
