1. Chemical pathology lab Flashcards
How does an increase in body temperature affect metabolism?
Increased metabolism (speeds up immune response)
What 3 tests are done in chemical pathology?
- Liver function test - albumin, total bilirubin, alkaline phosphatase (ALP), alanine amino-transferase (ALT)
- Urea and electrolytes - Na, K, urea, creatinine
- Blood glucose
Who can take blood at a GP?
- GP
- Practice nurse
- Junior doctor
- Medical student
What happens if you fill the wrong tube with blood?
Throw it away
What does a blood tube with a red top contain?
Nothing
• blood will clot within 5 minutes
What does a blood tube with a yellow top contain?
Gel to speed up clotting
• helpful to separate serum and red cells
What does a blood tube with a purple top contain?
Potassium EDTA
• anticoagulant, preserves red cells for 6 hours
What does a blood tube with a grey top contain?
Fluoride oxalate
• poison, kills red cells, stops anaerobic respiration so gives true glucose result
• otherwise would be falsely low
Which blood tube do you use for U+E (urea and electrolytes)?
Serum in yellow/red top
Which blood tube do you use for HbA1c?
Plasma in purple top (more HbA1c, worse diabetes)
Which blood tube do you use for a thyroid function test (FT)?
Serum in yellow/red top
Which blood tube do you use for liver function tests?
Yellow/red top
If you perform electrophoresis on red cells, what does the HbA band look like in diabetes and why?
• Blurred band
• Haemoglobin is glycated
• Glucose sticks to the haemoglobin randomly (more glucose, more sticking, broader band)
(• same happens with HbA1c)
What’s the difference between serum and plasma?
- Serum - no clotting factors
* Plasma - has clotting factors
How can you obtain serum from a blood test?
- Mix blood with no anticoagulant
- Blood will clot
- Clotting factors are consumed
- Clot can be removed, serum is left behind
What happens to the clotting factors if you use an anticoagulant, and how can blood be separated then?
- Clotting factors are unused
* Separation into red cells and plasma with a centrifuge
What does a green top blood tube contain?
Heparin
What does a blue top blood tube contain, what is it used for and how?
- Citrate
- Anticoagulant - removes calcium, preventing clotting
- Used to measure clotting factors
- Need to be filled to the top
- Remove sample => add calcium => blood clots - measure time taken to clot
- Can measure PT (prothrombin time) or PTTK (partial thromboplastin time)
When do you contact the chemical pathologist?
- Want sample rapidly centrifuged out of hours
- Want to measure labile hormones e.g. insulin (breaks down quickly)
- Urgently need CSF glucose and protein to be measured
Where are blood test results available?
- Computer
* If urgent - communicated to requesting clinician by telephone
What should come to mind when you see low Na and high K?
Primary adrenocortical failure -> aldosterone problem
What happens to the blood cells if you take blood from a difficult vein, and the needle is small?
- Damaged as they squeeze through the needle
- Haemolysis
- High K as red cells contain a lot
What can you measure to test renal function?
- Creatinine - marker of GFR (very little absorbed or secreted by tubules)
- Urea - rises when patient is dehydrated
Are liver enzymes meant to leak into the blood?
Normally only a tiny amount
What happens to ALT (alanine amino-transferase) in viral hepatitis?
Elevated
What happens to ALP (alkaline phosphatase) in a liver/biliary obstruction?
Elevated
How can you tell if someone has high bilirubin?
Jaundice
What are the cardiac enzymes that can be measured?
- Troponins - if high, definitely a problem
- Creatine kinase (CK) - muscle damage, not specific for cardiac muscle
- Aspartate amino transferase (AST) - also in the liver
- Lactate dehydrogenase (LDH) - also in the liver
