Chemical Pathology - Enzymes + Cardiac Markers

Question 1

What condition causes high serum levels of amylase (~>10x upper limit)?

Answer 1

Acute pancreatitis

Question 2

What are some non-specific causes of a raised serum amylase?

Answer 2

• Renal insufficiency
• Intestinal infarct/peritonitis
• Cholecystitis
• Salpingitis
• Ectopic pregnancy
• Abdominal cancers

Question 3

What condition is highly indicative if it’s >3x the upper limit of lipase?

Answer 3

Acute pancreatitis

Question 4

Which is more specific in diagnosing acute pancreatitis, amylase or lipase?

Answer 4

Lipase

Question 5

What conditions can see a raised lipase?

Answer 5

• Renal linsufficiency
• Small intestinal ischaemia/obstruction
• Sepsis
• DKA
• Cholecystitis

Question 6

What is the most widley used marker of muscle damage?

Answer 6

Creatine Kinase

Question 7

What Creatine Kinase markers are there and what high levels indicate?

Answer 7

CK-MM = skeletal muscle

CK-MB (1+2) = Cardiac muscle (re-infarcts)

Question 8

What are physiological causes of a raised creatine kinase?

Answer 8

Afro-caribbean (<5x upper normal limit)

Question 9

What are some pathological causes of a raised creatine kinase?

Answer 9

• Duchenne Muscular Dystrophy (>10x ULN)
• MI (>10x ULN)
• Rhabdomyolysis
• Statin-related myopathy

Question 10

What urine sign is seen in rhabdomyolysis?

Answer 10

Tea-stained urine

Question 11

What marker is good at detecting re-infarcts?

Answer 11

Myoglobin

Question 12

What is statin-related myopathy and some RFs?

Answer 12

• Spectrum of myalgia to rhabdomyolisis secondary to taking statins

RFs:
- High dose
- Genetic predisposition
- Prev. Hx of myopathy with another statin

Reversible increase in CK

Question 13

Where is Alkaline Phosphatase present in high concentrations?

Answer 13

• Liver
• Bone
• Intestine
• Placenta

Question 14

How can you differentiate between liver + bone ALP?

Answer 14

• Rise in GGT (liver)
• Electrophoresis
• Bone-specific assay of ALP

Question 15

What are some physiological causes of a raised ALP?

Answer 15

• Pregnancy (3rd trimester)
• Childhood (during growth spurts)

Question 16

What are some pathological causes of a raised ALP?

Answer 16

> 5x ULN:
- Bone: Paget’s, Osteomalacia
- Liver: Cholestasis, Cirrhosis, Obstructive Jaundice

<5x ULN:
- Bone: Tumours, Fractures, Osteomyelitis
- Liver: Infiltrative Diseases, Hepatitis

Question 17

When is Brain natriuretic peptide raised?

Answer 17

Heart Failure (>400 = highly sensitive, <100 = exclude)

Question 18

What is brain natriuretic peptide?

Answer 18

• A hormone that is primarily released from the ventricles in the heart
• Released in response to ventricular stretch
• Roles in reducing systemic vasoconstriction, sodium retention + renal sympathetic activity

Question 19

What is a confounding factor to interpretation of a raised brain natriuretic peptide?

Answer 19

CKD

Question 20

What are some pros to NT-proBNP?

Answer 20

• More sensitive than BNP
• Greater prognostic value

Question 21

What is troponin?

Answer 21

NOT AN ENZYME
- Myocardial injury marker
- Protein which forms part of the contractile apparatus in cardiomyocytes, released during an MI

Question 22

When is troponin measured?

Answer 22

6 + 12 hours post-onset of pain
- 100% sen + 98% spe at 12-24hrs

Question 23

How long does troponin remain elevated for?

Answer 23

3-10 days

Question 24

What conditions (aside from MI) see a raised troponin?

Answer 24

• Coronary spasm
• Coronary dissection
• PCI
• Myocarditis
• PE
• HF
• Cardiomyopathies
• Sepsis
• Cardiac surgery
• Chest trauma
• Defibrillation

Question 25

What is an international unit?

Answer 25

• 1 international unit is the quantity of enzyme that catalyses 1uMol of substrate in a minute (at given temperature + pH)
• Measure of enzyme activity (not mass or concentration)