Introduction and chemical pathology lab Flashcards
What are the different tubes for collecting blood and what do they contain?
Red top= no anticoagulant Yellow top= have gel to speed up clot Purple top= have potassium EDTA Grey top= have fluoride oxalate (poison) Blue top= citrate (anticoagulant)
What does the potassium EDTA do?
It keeps the cells alive and stops blood clotting -
What does fluoride oxalate do and when is it used?
Poison to red blood cells, it is used if you want to measure blood glucose- if cells are alive they will consume glucose
What is HbA1c?
Glycated haemoglobin
-haemoglobin with glucose attached to it and is a measure of glucose in blood over a longer period (3 months_
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
plasma = serum + clotting factors
What is serum useful for measuring?
Electrolytes
How would you get just the serum from the blood?
Add it to a yellow 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,
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- needs to be discarded
Why is citrate useful as an anticoagulant?
It is reversible
What is citrate used to measure?
Clotting factors
How does citrate act as an anticoagulant?
It binds to calcium and prevents clotting
How do you measure clotting factors once you have a sample in the citrate bottle?
Clotting factors: blue tube. It has citrate which removes calcium to prevent clotting. You must fill it to the top. (from which you get APTT or PT when you add calcium
When do you need to contact a chemical pathologist?
- need sample to be rapidly centrifuged out of hours
- need to measure labile hormones such as insulin
- urgently need CSF glucose and protein to be measured as 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
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
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
