Blood Laboratory Tests 2

Question 1

What are liver function tests

Answer 1

Liver function tests provide information on the health and functionality of the liver

Question 2

What can liver function tests provide information on (3)

Answer 2

1. The synthetic function of the liver
2. The metabolic function of the liver
3. The health of hepatocytes (liver cells)

Question 3

What do liver function tests consist of (3)

Answer 3

1. Liver enzymes (ALT/AST, GGT, ALP)
2. Hepatic proteins (albumin, globulin, clotting factors)
3. Bilirubin

Question 4

What are hepatic enzymes (4)

Answer 4

1. These enzymes are involved in the metabolic pathways of the liver
2. They are intracellular enzymes, so blood levels are raised if hepatocytes are damaged or there are other issues (such as blockages)
3. Significant elevation can indicate acute liver injury but correlating results with hepatic metabolic capacity is difficult
4. These enzymes are not exclusively found in the liver

Question 5

What do hepatic enzymes consist of (4)

Answer 5

1. Alanine transaminase (ALT) / aspartate transaminase (AST)
2. Alkaline phosphatase (ALP)
3. Gamma-glutamyl transpeptidase (GGT)

Question 6

What do hepatic proteins do (2)

Answer 6

1. albumin and globulin
2. provide a marker of the synthetic capacity of the liver

Question 7

What causes hypoalbuminaemia (4)

Answer 7

1. reduced albumin synthesis
2. Liver disease
3. Malnutrition
4. Pregnancy

Question 8

Where is albumin located

Answer 8

in the extracellular fluid and contributes to oncotic pressure

Question 9

How does albumin affect drug binding (3)

Answer 9

1. Many drugs bind to albumin, but some (e.g. phenytoin) are highly protein-bound
2. Only unbound ‘free’ drug is active
3. Hypoalbuminaemia (low albumin) can increase the concentration of unbound active drug

Question 10

What is prothrombin (4)

Answer 10

1. a clotting factor produced in the liver
2. Production of prothrombin is reduced in liver disease, so it takes longer for blood to clot, increasing risk of bleeding
3. Prothrombin time (PT) is a blood test used to indicate how long it takes in seconds for blood to clot in lab conditions
4. Prothrombin time is also expressed as a ratio compared to a standard control (INR)

Question 11

What is the INR (3)

Answer 11

1. International normalised ratio = patent’s PT / control PT
2. an indicator of hepatic protein synthesis
3. most commonly used to monitor oral anticoagulant therapy (warfarin)

Question 12

What is bilirubin (2)

Answer 12

1. Bilirubin is a breakdown product of haemoglobin
2. which is metabolised and excreted in the liver mainly via the faeces

Question 13

What can elevated bilirubin lead to (2)

Answer 13

1. hyperbilirubinaemia
2. jaundice

Question 14

What can elevated bilirubin be caused by (3)

Answer 14

1. Liver disease
2. Haemolysis
3. Obstruction of the bile duct

Question 15

What is a full blood count

Answer 15

Full blood count is a haematological test that examines the make-up of the blood cells

Question 16

What can the full blood count be used to diagnose (3)

Answer 16

1. Anaemias
2. Infection
3. Blood disorders

Question 17

What components does a full blood count consist of (6)

Answer 17

1. Haemoglobin
2. Red cell count
3. Mean corpuscular (cell) volume
4. White cell count
5. Neutrophils
6. Platelet count

Question 18

What are other common blood tests (9)

Answer 18

1. Capillary blood glucose and HbA1c
2. Cholesterol
3. D-dimer
4. Troponin T and troponin I
5. Thyroid function tests
6. Serum cortisol
7. TPMT
8. Vitamin levels
9. Blood cultures

Question 19

What is therapeutic drug monitoring

Answer 19

involves assays that determine the concentration of a given drug in the serum

Question 20

What are the uses of therapeutic drug monitoring (3)

Answer 20

1. To assess for toxicity/overdose (e.g. paracetamol levels)
2. To check for adherence (e.g. sodium valproate therapy)
3. To monitor the levels of drugs with a narrow therapeutic window

Question 21

What are examples of drugs with a narrow therapeutic window (7)

Answer 21

1. Aminoglyosides (e.g. gentamicin)
2. Glycopeptides (e.g. vancomycin)
3. Cardiac glycosides (e.g. digoxin)
4. Methylxanthines (e.g. theophylline)
5. Phenytoin
6. Alcohol
7. Lithium

Question 22

What are general tips for interpreting blood tests (6)

Answer 22

1. Quoted reference ranges are based on population averages and so some people naturally sit outside of these
2. Slight abnormalities often don’t require any corrective action
3. It’s often more helpful to look for trends rather than isolated results
4. Always consider the clinical status of the patient
5. A patient with chronic kidney disease is always going to have a raised SrCr so we only need to be concerned if the results are acutely different from the patient’s ‘normal’ results
6. Always treat the patient, not a number (e.g. if a patient’s digoxin level is low but their heart rate is controlled then there is no need to intervene)

Question 23

Blood is usually drawn from which site for laboratory testing

Answer 23

Anticubital fossa (ACF)

Question 24

Which electrolyte is most critical for maintaining normal cardiac function

Answer 24

Potassium

Question 25

A patient has an estimated creatinine clearance (eCrCl) of 21 mL/min. What does this indicate?

Answer 25

Severe renal impairment

Question 26

Hypophosphatemia (low phosphate levels) is commonly caused by

Answer 26

Chronic kidney disease