Lab Diagnostics Methods

Question 1

A patient presents with fever, rash, lymphadenopathy and diarrhoea. What are these an indication of?

Answer 1

Fever is a sign of some sort of inflammatory response. Together with rash and lymphadenopathy + diarrhoea suggests a viral infection e.g. glandular fever

Question 2

What is ESR and how does it change in infection?

Answer 2

Erythrocyte Sedimentation Rate – the rate at which red blood cells settle out of suspension in blood plasma, measured under standard conditions
ESR increases in infection

Question 3

What are the four tube colours for blood collection and what do the colours mean?

Answer 3

Red – no anticoagulant
Yellow – gel – makes the coagulation occur faster
Purple – potassium EDTA (keeps cell alive e.g. if want to do a cell count)
Grey – fluoride oxalate (kills cells e.g. if want to measure blood glucose don’t want RBCs utilising the blood glucose)

Question 4

What are the purple cap bottles used for?

Answer 4

Potassium EDTA keeps the cells alive

It is used when measuring cell counts or anything in general to do with the cells

Question 5

What are the grey cap bottles used for?

Answer 5

Fluoride oxalate kills the red blood cells – this is used for measuring blood glucose because live red blood cells will consume the glucose

Question 6

Which bottle is used for measuring HbA1c?

Answer 6

Purple Top – potassium EDTA

Question 7

Why is HbA1c useful cf. measuring blood glucose?

Answer 7

RBCs survive for ~120 days thus Hb1Ac gives you a measure of blood glucose over ~a 3 month period. An elevated hbA1c suggests poorly controlled blood glucose

Question 8

What is the difference between serum, blood and plasma

Answer 8

Blood describes all the constituents together
Plasma describes the solution once cells are removed
Serum is the plasma with proteins removed (including clotting factors)

Question 9

How can you produce serum? What should the experimenter be wary of?

Answer 9

Allow for blood to coagulate. Centrifuge. Can separate the plasma from clotted blood + layers of cells . But note have to be careful a syringe can disrupt the layers promoting haemolysis and a spike in K+ in plasma. This would give a reading incompatible with life.

Question 10

What is creatinine a marker of?

Answer 10

Renal function (GFR) – it is produced by the body at a constant rate and it is excreted at a constant rate provided that the kidneys are functioning normally

Question 11

If urea is elevated and creatinine is normal what is the clinical significance?

Answer 11

Suggests dehydration

Question 12

How would urea and creatine change in renal disease

Answer 12

Both would increase

Question 13

What does the combination of low Na and high K suggest?

Answer 13

Adrenal failure. E.g. in Addison’s disease observe high K, low Na, high urea and normal creatinine

Question 14

In liver function tests what are the main proteins we test for

Answer 14

Albumin 
Bilirubin 
Alkaline phosphatase 
Aspartate aminotransferase 
Alanine aminotransferase

Question 15

How does albumin change in liver disease?

Answer 15

It decreases because the liver can no longer produce more albumin

Question 16

How does bilirubin change in liver disease?

Answer 16

It would increase, because less is being effectively removed. This can lead to jaundice if levels go above 30 umol/L

Question 17

What happens to alkaline phosphatase during a bone fracture?

Answer 17

Osteoblasts produce lots of alkaline phosphatase. So during a bone fracture when they are producing more bone, ALP levels can rise.

Question 18

What happens to alkaline phosphatase, Aspartate aminotransferase and
Alanine aminotransferase during liver disease?

Answer 18

Both would increase i.e. generally get increased leakiness of proteins

Question 19

What is the first thing you do if a patient presents with heart attack type symptoms?

Answer 19

ECG

Question 20

What is measure to confirm a heart attack following an ECG?

Answer 20

Measure troponin levels

Question 21

What else could cause heart attack type symptoms?

Answer 21

Peptic ulcer commonly causes similar pain distirbution. Need to be careful because thrombolytics would make the bleeding worse.

Question 22

What do you want to be wary of when you have a patient presenting with heart attack symptoms that you suspect might be a peptic ulcer?

Answer 22

Giving thrombolytics can make the bleeding worse

Question 23

List the main cardiac enzymes used in experiments.

Answer 23

Troponins (these aren't enzymes! But mentioned here anyway)
Creatine Kinase (CK) Aspartate aminotransferase (AST) 
Lactate dehydrogenase (LDH)