chem path lab Flashcards
what tests are involved for chem path *
liver function test - LFT
urea and electrolytes
blood glucose
calcium and phosphate
hormone assays with endo -TSH, thyroxine, cortisol
what does a request form for labs look like *
pic
how do you take a sample *
label tube
venepuncture
important to get the right tube
what anticoagulants do differnet tubes have *
red - none
yellow - gel to speed up clot
purple - potassium EDtA
grey - fluoride oxalate - poison
what tube would you use for U adn E *
serum in yellow/red
what tube would you use to test glucose *
plasma in grey
what tube would you use to test HBA1c *
plasma in purple
what tube would you use for thyroid function tests *
serum in yellow/red
what tube would you use for LFT *
yellow/red
what is the erythrocyte sedimentation rate *
red cell settle in tube
how far go in 1 hr
if lots of inflamm cell and protein move at a faster rate
if high show somethings wrong
if normal - rule out things
why do you test for C reactive protein *
made by liver in infection
eg if high could be septicaemia
wat is tested for in liver function test *
liver release enzymes
if enzymes in blood = liver damaged
what is makes gammaGT *
liver
what happens in red tube
clot in 5min
centrifuge
get serum at the top with no clottomg factor
what happens in purple tube *
have EDTA
keeps cells alive
can do full blood count
also have K in - cant use it to measure electrolytes
what happens in grey tube *
oxalate is poisen - stops glycolysis, ie stop the red cells consuming the glucose - so measured glucose is correct
also stop clotting so have plasma with clotting factors
why would you measure HBA1c *
long term measure of glucose
glycated Hb
high blood glucose - 12%
marker of tissue damage in the heart and brain - tells you about long term glucose control
what happens in a yellow tube *
gel to speed up clot
Hb heavy - blood go to bottom
gel in the middle
leave serum at top
red cell loads of k in - dont want in serum when take sample
what is the difference between serum and plasma *
plasma has clotting factors
is it serum or plasma in red/yellow tubes *
blood clots using all clotting factors
clot can be removed
leaving serum
examples of anticoagulants and what happens if they are in tubes *
EDTA/heparin
clotting factor unused
blood can be separated into cells and plasma - centrifuge: if really fast have plasma at top, then lymphocytes and monocytes, then gel, tehn red cells and neutrophils
what are blue tubes used for *
measure amount of clotting factor
has citrate - make blood not clot
then add Ca - will clot - time taken to clot shows if have enough clotting factors
when do you need to contact the chemical pathologist *
when want the sample to be rapidly centrifuged out of hours
when you wnat to measure labile (rapidly broken down) hormones eg insulin - need to do in 15mins - otherwise clotting damages it
urgently need CSF glucose and protein to be measured - high protein and low glucose suggest bacteria in CSF eg with meningitis
what happens to samples *
chemistry carried out on plasma or serum - so need to centrifuge to separate plasma/serum from red cells
how do you get the results from chem path *
on computer
if urgent - phoned to clinician
how are reference ranges determined *
take 100 healthy people
bottom and top level were…
this is the reference range
what is a cause of low Na and high K
low aldosterone
how can haemolysis of red cells occur,
what is the consequence *
red cell lyse as go through needle
cause high K in sample - because would have been in RBC
tell because plasma is a rose colour
decribe what you are looking for with urea and creatine *
made by the muscle and excreted by kidney
creatine - filitered but not absorbed - give the glomular filtrate rate
normal creatinine means the kidneys are ok
high urea means tubules not working - because of severe dehydration - GFR stays normal until end so creatinine normal
in renal failure both urea and creatinine rise
what comes with experience when looking at liver function test
tell what disease the patient has from the pattern of the leak
what is included in ‘liver’ on a request sheet *
albumin - synth in liver
BR
alkaline phosphtase
ALT (alanine amino-transferase)
what would you tick on a request form for someone with jaundice *
liver
AST
gammaGT
how would you interpret liver function tests *
low albumin = liver failure
high BR - break down too many red cells, or problem with BR excretion
alkaline phosphtase high - something affecting bile flow - physical block
ALT high - inflammed liver, acute hep
high AST - inflam
how do you make a diagnosis *
take history
examine pt
make a plan - inc tests
why do you look at cardiac enzymes *
present in the heart muscle
during HA - heart muscle damaged
these enzymes leak into blood at huge amounts
tell if someone had HA
measure if someone has a history of heart disease
might not feel HA - eg diabetic neuropathy
what are the cardiac enzymes and what do they show *
troponins
creatine kinase (CK)
aspartate amino transferase (AST)
lactate dehydrogenase (LDH)
can look at pattern to see when MI happened:
troponin and CK raise in hours of MI
AST - next day
LDH - after days
AST liver enzyme too - so heart/live rdamage rise AST
what do you tick on a request form for cardiac enzymes *
heart
AST
role of a chemical pathologist
work in chem path lab
metabolic medicine clinics
research into better ways of getting results
