Introduction and chemical pathology lab Flashcards
What are the different tubes for collecting blood and what anticoagulants do they contain?
Red top= no anticoagulant
Yellow top= have gel to speed up clot
Purple top= have potassium EDTA for a full blood count - keeps cells alive so is ideal for haematology
Grey top= have fluoride oxalate (poison) stops the cells metabolising so you can measure serum glucose at the time
Blue top= citrate (anticoagulant)
Green top = heparin
What does the potassium EDTA do?
It keeps the cells alive- what you want if you want to do anything with the cells (red, white and platelets)
What does fluoride oxalate do and when is it used?
It poisons red blood cells so that glucose levels stabilise, otherwise the red cells will consume the glucose
What is HbA1c?
Glycated haemoglobin
What would you expect to find in terms of HbA1c when performing electrophoresis on the blood of someone with poorly controlled diabetes?
More HbA1c which will be found at bottom
For what period of time does the electrophoresis show you how good blood glucose control has been?
3 months because that’s how long red blood cells survive
What is the difference between serum and plasma?
Serum contains no clotting factors
Extraction of serum : yellow/red top–> blood clots using up all factors –> clot can be removed leaving serum which is yellow
Plasma separation: Purple or green top–> natural clotting factors are left unused–> blood separated by centrifugation –> plasma is the top layer
What is serum useful for measuring?
Electrolytes
How would you get just the serum from the blood?
Add it to a yellow/red top tube, the gel will speed up coagulation and use up all the clotting factors, the serum and cells are then separated by centrifuge because the cells are more dense than the gel and the gel is more dense than the serum so it separates the two, you can then use a tube to just suck out the serum
What is a problem with poor blood collection?
Cells are full of potassium
If you do a poor collection and pull hard on syringe you will lyse cells and there will be extra potassium in the plasma which will affect results- you can notice it because it looks pink
Why is citrate useful as an anticoagulant? What does it measure?
It is reversible
Clotting factors
How does citrate act as an anticoagulant?
It binds to calcium and prevents clotting
When do you need to contact a chemical pathologist?
When you want a sample to be rapidly centrifuged out of hours
When you want to measure labile hormones such as insulin (broken down in tube over time as blood clots so spin the sample to suck off serum within 30min then freeze so that the insulin survives)
When you urgently need CSF glucose and protein to be measured
Meningitis- if there is bacteria they will consume glucose
If someones results contained low sodium and high potassium what would you consider?
Adrenal failure
What is the link between urea and creatinine?
The kidneys excrete both
Where is creatinine produced?
In the muscle and produced constantly
Why does the amount of creatinine that you produce stay the same through adult life?
Your muscle mass normally roughly stays the same
As the creatinine production rate is fixed, what does the level of creatinine in the blood show you?
How well your kidneys are functioning- marker of GFR (very little is absorbed or secreted by the tubules)
How much do urea levels vary?
A little bit depending on your diet- it comes from protein
What is urea a marker of?
How dehydrated you are but GFR stays the same to the end
What happens in the kidney when you are dehydrated in terms of urea?
You start reabsorbing more water and accidentally absorb some urea
If someone had high urea and normal creatine, what would you suspect?
Dehydrated with normal kidney function
What will happen to urea and creatine levels in renal disease/kidney failure ?
Urea and creatinine rise
What will your potassium, sodium, urea and creatine levels be like in addison’s disease?
High potassium
Low sodium
High urea
Normal creatine
Where are liver enzyme found?
In the liver within hepatocytes
Tiny amount leaks into blood
In terms of liver enzymes, what happens during liver disease?
More leak into the blood
What common enzymes are measured in liver function tests?
Albumin (synthesised in Liver)
Bilirubin
Alkaline phosphatase (ALP)
Alanine Aminotransferase (ALT)
Also:
GGT
Aminotransferase/Transaminase (AST)
What is TBil?
Total bilirubin (excreted in the faeces through bile) (increases with liver failure or biliary tree problems)
What happens when the liver fails (in terms of albumin)?
Liver albumin will fall
What is the first thing you do when you have a patient presenting with heart attack type symptoms?
ECG to see if they’re having an acute heart attack
If you suspect a heart attack, what enzyme do you check?
Troponin
What other cardiac enzymes are there which will be elevated when there is damage to the heart muscle?
Troponin Creatinine kinase(CK) Aspartate aminotransferase (AST) Lactate dehydrogenase (LDH)
What bottles would these samples be collected in? U&E Glucose HBA1C TFT (thyroid function test) Liver function tests
U&E - serum in yellow/red top Glucose - plasma in grey top HBA1C - plasma in purple top - if HBA1C is glycates the glycose sticks to Hb --> Hb is heavier --> moves less on electrophoresis; poorly controlled diabetes --> more HBA1c + stronger band TFT - serum in yellow/red top Liver function tests - in yellow/red top
What causes cardiac enzymes to rise in a heart attack?
Cardiac enzymes are present in heart muscle
During a MI–> muscle is damages
Enzymes leak out into blood in large amounts
Good indicators of a heart attack
List some common diagnostic tests.
- FBC (full blood count), ESR, CRP
- LFTs (liver function)
- U&Es (urea & electrolytes)
- Blood Glucose
- Investigate viral illnesses
- Stool culture - Bacteriology
Why will the glucose reading of blood be lower when it has been left out?
Anaerobic glycolysis occurs
Red cells consume glucose
(this can be prevented by fluoride oxalate poison)
What can be the cause of hyperkalaemia in a blood sample?
May be due to haemolysis of red blood cells
