Lecture 1: Intro Flashcards
Which tests are done by the chemical pathology lab
U&E (Urea, Na+, K+, Creatinine)
LFT (Alb, ALP, ALT)
Blood glucose
What to request in stool
Microscopy
Culture
Sensitivity (to work out antibiotic)
What tests involved in LFT
Albulin, Bilirubin, alkaline phosphatase (different isoenzymes for bone and liver), ALT
What is in each of the following tubes: Red Yellow Purple Grey
What would you put the following tests in:
U&E Glucose HBA1c TFT Liver function tests
Red: nothing
Yellow: gel to increase clotting (separates out plasma and cells)
Purple: Potassium EDTA (anticoagulant)
Grey top: Flouride oxalate (poison)
U&E : serum in yellow/red top
Glucose: plasma in grey top
HBA1c: plasma in purple top
TFT: serum in yellow/red top
Liver function tests: in yellow/red top
How to measure glucose in blood
Red cells consume glucose (anaerobic glycolysis), so the longer this is left out, the lower the glucose may read
Fluoride Oxalate (poison) prevents the red cells from using glucose
High K+ and low Na+
shows adrenal failure perhaps
What would high urea with normal creatinine show
could show dehydrated…. urea doesn’t show much about kidney health… creatinine shows more shows more about GFR
What is postassium EDTA and what tubes have this
This is a strong anticoagulant and these tubes are usually used for complete blood count
PURPLE
What colour bottle for flouride oxalate
Grey top (=poison)
What do red and yellow top bottles contain
red- nothing
yellow top- have gel to speed up clot
When would you use a purple tube
When looking at plasma, or for haematology (red cells)
Differentiate serum and plasma
Serum is that part of blood which is similar in composition with plasma but exclude clotting factors of blood.
Give 2 examples of anticoagulants used in bloods
What do you use if you want to measure clotting factors
EDTA (purple) or heparin (green)
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)
In which case would you get plasma when doing bloods, and when would you get serum
Serum: if the clotting factors are used up, i.e. in a red or yellow top, then there are no clotting factors in the centrifuged sample
Plasma: if the clotting factors are not used up (i.e. if you give EDTA, purple top) then you will get clotting factors contained in the serum (i.e. PLASMA) during centrifuge.
You use red/yellow for biochemistry. Yellow is good because there is no risk of red cell contamination (the red cells are separated from the serum by the gel), which is good because red cells have lots of K+ and other stuff that could affect the biochemistry results
Reference range for Na K U Cr
Na+: 135 – 145
K: 3.5 – 5.0
U: 2.0 – 6.0
Cr: NR 70 – 120
High potassium what could be the cause
Could be adrenal failure
OR
could be haemolysed sample (i.e. RBCs split open in the sample, which would them increase the potassium massively)
What is creatinine a arker of
GFR
What happens to creatinine and urea in renal failure
What about dehydration
Urea and creatinine increase in renal failure
Creatinine marker of GFR. Very little secreted or absorbed by tubules
Urea increases when patent is deydrated by GFR stays the same to the end
This is becasue during dehydration, water reabsorbed and so will urea, but creatinine is too big to be absorbed
What enzymes and other molecules are looked at in LFT
Albumin: synthesised in the liver
Bilirubin
Alkaline Phosphatase. Increased in obstruction i.e. due to cancer
ALT (alanine amino-transferase). This enzyme performs gluconeogenesis. If high, it means the enzyme has leaked into the circulation. Viral hepatitis.
What other enzyms would you measure in a patient with jaundice
AST and GGT
What are the cardiac enzymes
Troponins
Creatine kinase (CK)
Aspartate amino transferase (AST)
Lactate Dehydrogenase (LDH)
Talk about AST and ALP. in terms of specificity and when they are raised
AST not speciifc to liver…. when raised it indicated peri-portal damage (i.e. damage to cells around the portal triad)
ALP is more speciic to liver…..
They don’t indicated liver FUNCTION, they indicate DAMAGE level, as they are released due to hepatocellular damage due to inflammation
When might albulin be low
CHRONIC liver injury (as albulin as 20 day half life so takes a while for it to fall)
When would you need to contact chemical pathologist
To rapidly centrifuge out of hours
To measure labile hormones like insulin (yellow top)
When you need CSF glucose and protein to be measured urgently
What might CSF look like if meningitis
Glucose low (bacteria using it)
Protein high
