Lecture 1: Intro

Question 1

Which tests are done by the chemical pathology lab

Answer 1

U&E (Urea, Na+, K+, Creatinine)

LFT (Alb, ALP, ALT)

Blood glucose

Question 2

What to request in stool

Answer 2

Microscopy
Culture
Sensitivity (to work out antibiotic)

Question 3

What tests involved in LFT

Answer 3

Albulin, Bilirubin, alkaline phosphatase (different isoenzymes for bone and liver), ALT

Question 4

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

Answer 4

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

Question 5

How to measure glucose in blood

Answer 5

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

Question 6

High K+ and low Na+

Answer 6

shows adrenal failure perhaps

Question 7

What would high urea with normal creatinine show

Answer 7

could show dehydrated…. urea doesn’t show much about kidney health… creatinine shows more shows more about GFR

Question 8

What is postassium EDTA and what tubes have this

Answer 8

This is a strong anticoagulant and these tubes are usually used for complete blood count

PURPLE

Question 9

What colour bottle for flouride oxalate

Answer 9

Grey top (=poison)

Question 10

What do red and yellow top bottles contain

Answer 10

red- nothing

yellow top- have gel to speed up clot

Question 11

When would you use a purple tube

Answer 11

When looking at plasma, or for haematology (red cells)

Question 12

Differentiate serum and plasma

Answer 12

Serum is that part of blood which is similar in composition with plasma but exclude clotting factors of blood.

Question 13

Give 2 examples of anticoagulants used in bloods

What do you use if you want to measure clotting factors

Answer 13

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)

Question 14

In which case would you get plasma when doing bloods, and when would you get serum

Answer 14

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

Question 15

Reference range for 
Na 
K 
U 
Cr

Answer 15

Na+: 135 – 145
K: 3.5 – 5.0
U: 2.0 – 6.0
Cr: NR 70 – 120

Question 16

High potassium what could be the cause

Answer 16

Could be adrenal failure

OR

could be haemolysed sample (i.e. RBCs split open in the sample, which would them increase the potassium massively)

Question 17

What is creatinine a arker of

Answer 17

GFR

Question 18

What happens to creatinine and urea in renal failure

What about dehydration

Answer 18

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

Question 19

What enzymes and other molecules are looked at in LFT

Answer 19

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.

Question 20

What other enzyms would you measure in a patient with jaundice

Answer 20

AST and GGT

Question 21

What are the cardiac enzymes

Answer 21

Troponins
Creatine kinase (CK)
Aspartate amino transferase (AST)
Lactate Dehydrogenase (LDH)

Question 22

Talk about AST and ALP. in terms of specificity and when they are raised

Answer 22

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

Question 23

When might albulin be low

Answer 23

CHRONIC liver injury (as albulin as 20 day half life so takes a while for it to fall)

Question 24

When would you need to contact chemical pathologist

Answer 24

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

Question 25

What might CSF look like if meningitis

Answer 25

Glucose low (bacteria using it)

Protein high