Introduction and Chemical Pathology Lab Flashcards
what tests should the doctor order for the following symptoms?
what does a fever suggest?
infection is the likely cause
- There are some autoimmune conditions that cause fever because fever is NOT caused by the organism but is instead caused by the immune response
what is the ESR? Erythrocyte Sedimentation Rate
what happens to ESR in infection?
the rate at which red blood cells settle out of suspension in blood plasma, measured under standardized conditions
- the ESR increases in infection
what tests are done by chemical pathologists?
LFTs - liver function tests
U&E - urea and creatinine
Blood glucose
what do the different colours of tubes for collecting blood mean?
different colored tops have different anticoagulants in them
- red top = no anticoagulant
- yellow top = have a gel to speed up the clot
- purple top = have potassium EDTA
- grey top = has fluoride oxalate (poison)
what does potassium EDTA do?
keeps the cells alive if you want to test the cells you must keep them alive
what does fluoride oxalate do?
is a type of poison that kills the red blood cells
- needed if we want to measure blood glucose
- if red cells are alive they will consume glucose so not accurate
what is HbA1c mean?
- If glucose sticks to the hemoglobin it becomes a bit heavier and its movement slows down
- so when you do electrophoresis
- patients with poorly controlled diabetes there is more HbA1c
- as RBCs survive 3 months it shows the last 3 months of glucose control
what What’s the difference between serum and plasma?
- if there is no anticoagulant in the tube the blood tends to clot
- when it clots all the clotting factors are used up so when we remove the clot we are just left with serum
- the serum has no clotting factors
why is serum useful and how to extract it?
- the serum is useful for measuring electrolytes
- the blood is centrifuged
- the clotting gel induces clotting
- the gel is arranged so it is denser than the serum, so the serum is preserved
what might happen if one carries out a poor blood collection?
(potassium)
- if you pull too hard on the syringe the blood collection might be poor
- the cells will become lysed
- if the RBCs haemolyse there will be extra potassium in the plasma
- you can notice this extra potassium as it will make the sample will appear pink
- the machine will dispose of the sample as this level of potassium is incompatible with life
what substances inhibit clotting factors?
EDTA and heparin
why is citrate used (blue top)
- citrate is another anticoagulant
- it is useful because it is reversible
- it is used to measure clotting factors
- citrate binds to calcium and prevents it from clotting
- calcium is needed to start the clotting process
- we are then able to measure the time of clotting process
why must we use fluoride oxalate when measuring glucose?
- fluoride oxalate kills the red cells which prevent them from taking up the glucose
- red cells take up glucose so the longer it is left out the lower the glucose is read
when do we need to contact a chemical pathologist?
- when the sample needs to be looked at rapidly out of hours
- When you want to measure labile hormones such as insulin
- when you need cerebral spinal fluid glucose and protein to be measured urgently
analyse the following results : insert the pic looking at the sodium and potassium
- sodium is low
- potassium is high
with this combination maybe adrenal failure (beware of haemolysis as this might give a high potassium reading)
- the urea is high and the creatinine is normal
urea shows hydration , creatinine shows how well kidneys are working
what does creatintine show?
- creatinine is excreted by the kidneys
- creatinine is produced by the muscle
- in adults, muscle mass remains roughly the same so the amount of creatinine one is making remains the same
- the level of creatinine in the blood shows the functioning of the kidneys
what does urea show?
- Urea is a marker of how DEHYDRATED you are
- When you are dehydrated, the kidneys start reabsorbing more water and accidentally absorbs some urea by ADH
- so dehydration causes high Urea
what happens to urea and creatinine in kidney disease`?
what happens to urea and creatinine in dehydration?
urea and creatinine concentrations will rise
urea will rise, creatinine will remain the same
where are liver enzymes present?
- Present in the liver (within hepatocytes)
- A tiny amount normally leaks in to the blood
what happens to the liver enzymes in liver disease?
more of these enzymes leak into the blood
what are popular enzymes measured in liver function tests?
Alanine Aminotransferase (ALT)
Aspartate Aminotransferase/Transaminase (AST)
Alkaline Phosphatase (ALP)
what is TBil?
what results in high TBil
Total Bilirubin - (excreted in the faeces through the bile)
- If there is something wrong with the liver or the biliary tree then bile will leak into the blood so you get high bilirubin
what is liver albumin for?
if the liver fails albumin falls
