Chemical Pathology Lab

Question 1

Possible causes of fever, rash and lymphadenopathy?

Answer 1

Viral illness e.g. Glandular fever

Question 2

Possible causes of diarrhoea?

Answer 2

Virus
Bacteria
Parasites

Question 3

Possible tests that a GP can do for Billy (OneNote!)?

Answer 3

o FBC (normally ALWAYS do one)

o ESR - erythrocyte sedimentation rate

• see how the quickly the RBCs settle in a tube
• if HIGH ESR (settles fast) = indication of inflammation

o CRP

• made by the liver in response to inflammation
• w. normal range of <10

o LFTs (liver function tests)
 - enzymes leak out e.g. ALP

o U&Es (urea and electrolytes)

o Blood glucose
o Stool culture

Question 4

Different tubes and their anticoagulants?

Answer 4

o RED = NO anticoagulant

o YELLOW = GEL
- to SPEED-UP clotting

o PURPLE = potassium EDTA

• STOPS blood from clotting
• thus preserves the cells

o GREY = fluoride oxalate (poison)

• poison to RBCs
• used when want to measure BLOOD GLUCOSE
• as if cells were alive, would consume glucose in blood continuously via. glycolysis

Question 5

Different between serum vs. plasma?

Answer 5

Serum = NO clotting factors
i.e. when the blood uses up all clotting factors and clots are removed

o after being in centrifuge w. special gel, blood separates
o top layer = serum
o bottom layer = clots

Plasma = SERUM + CLOTTING FACTORS (clotting prevented)

Question 6

Tests and their associated tubes?

Answer 6

o U&E

• SERUM
• Yellow OR Red tube

o Glucose

• PLASMA
• Grey

o HBA1C
- PLASMA
- Purple
This Hb has a glucose attached to it so is a MEASURE of glucose in the blood over a longer period (3-months)

o TFT (thyroid function tests)

• SERUM
• Yellow OR Red tube

o LFTs
- Yellow OR Red tube

Question 7

Anticoagulant normally used to obtain Plasma?

Answer 7

o EDTA

o Heparin

Question 8

How are anticoagulants used in collecting samples?

Answer 8

The clotting factors remain UNUSED

o the blood can be separated into RBCs & plasma (with clotting factors still in)

Question 9

Another anticoagulant that can be used?

Answer 9

Citrate (blue top!)

It is REVERSIBLE
Used to measure clotting factor levels (PT and aPTT via. Ca2+ & citrate bonding)

Question 10

Why is fluoride oxalate used?

Answer 10

GREY tube!

RBCs consume glucose (anaerobic respiration) SO the longer it is left, the lower the glucose may read

Question 11

Why should you beware of haemolysis?

Answer 11

A poor blood collection can result in the haemolysis of RBCs entering the tube
o identified as the sample may be PINK
o collection is therefore discarded

Cells are FULL of K+ so haemolysis will confound K+ results

Question 12

When should you contact a chemical pathologist?

Answer 12

1. Need of rapid centrifuge OUT-OF-HOURS
2. Need to measure LABILE HORMONES e.g. plasma insulin (clotting factors could render it ineffective)
3. Urgently need CSF GLUCOSE & PROTEIN measured
   e. g. as meningitis will rapidly consume glucose

Question 13

NR for Na?

Answer 13

135 - 145

Question 14

NR for K?

Answer 14

3.5 - 5.0

Question 15

NR for U?

Answer 15

2.0 - 6.0

Question 16

Nr for Creatinine?

Answer 16

70 - 120

Question 17

If see LOW Na+ & HIGH K+ what is first thought?

Answer 17

Could be ADRENAL FAILURE (aldosterone issue!)

Beware - could be haemolysis contributing to HIGH K+!!

Question 18

Further tests show HIGH urea but NORMAL creatinine?

Answer 18

If RENAL FAILURE = BOTH RISE!

SO concentrated urine = DEHYDRATION!

Question 19

Creatinine and Urea?

Answer 19

Creatinine is measure of GFR - very little absorbed or secreted in tubules

Urea levels rise when patient DEHYDRATED but GFR stays the same
NOTE: Addison’s disease presents like this!

Question 20

How can liver disease be diagnosed?

Answer 20

via. Liver Enzymes

Small amount normally leaks into blood
BUT
in Liver disease MORE of these enzymes leak

Question 21

If suspect jaundice, along with LFTs what else should be measured?

Answer 21

AST - asparate aminotransferase
o In healthy individuals, levels of AST in the blood are low. When liver or muscle cells are injured, they release AST into the blood.

GGT - Gamma-glutamyl transferase
o When the liver is injured or the flow of bile is obstructed, the concentration of GGT within the bloodstream rises. It is therefore a useful marker for bile duct problems

Question 22

Enzymes normally measured in LFTs?

Answer 22

o ALT - alanine aminotransferase
o AST - asparate aminotransferase

o ALP - alkaline phosphatase

• POST-fracture, ALP will RISE
• this is as osteoblasts secrete ALP as they make new bone

o Albumin
o Bilirubin
- if this is HIGH, may be something wrong with the biliary tree

Question 23

How can cardiac enzymes be used clinically?

Answer 23

Post-MI, cardiac enzyme LEAK into blood like in the liver

Initally do ECG then check enzymes:
 o Troponins
 o CK (creatine kinase)
 o AST
 o LDH (lactate dehydrogenase)