Chemical Pathology 15 - Enzymes and cardiac markers

Question 1

What is the Km?

Answer 1

Michaelis Menten constant

= concentration of substrate at which the reaction velocity is 50% of maximum

Question 2

What tumour marker can be used for germ cell, ovarian and testicular malignancies?

Answer 2

ALP

Question 3

When is ALP elevated physiologically?

Answer 3

In pregnancy and childhood

Question 4

Recall 4 pathologies that can cause a raised ALP

Answer 4

1. Bile duct pathology (eg cholestatic liver disease)
2. Bone pathology (fracture/ metabolic bone disease)
3. Germ cell tumours
4. Intestinal pathology (but not routinely used for investigation of bowel disorders)

Question 5

Which LFT enzyme is most specific to liver pathology?

Answer 5

ALT

Question 6

How can hepatic and biliary disease be best distinguished on the LFTs?

Answer 6

ALT:ALP ratio

If ALT much higher than ALP = hepatic

Question 7

How many isoenzymes of LDH exist?

Answer 7

5

Question 8

Recall 3 things that a raised LDH may indicate

Answer 8

1. Haemolytic anaemia
2. Tumour marker (lymphoma, germ cell testicular Ca)
3. Myositis (rheum)

Question 9

Which enzyme is markedly raised in acute pancreatitis?

Answer 9

Serum amylase

Question 10

What is the most likely cause of a raised CK-MB1?

Answer 10

Rhabdomyolysis (history of long lie/ big fall?)

Question 11

Where is CK-MB1 vs CK-MB2 produced?

Answer 11

CK-MB1 - skeletal muscle

CK-MB2 - cardiac muscle

Question 12

In which population is CK physiologically slightly raised?

Answer 12

Afrocaribbean

Question 13

Which prescription drug may be the cause of a raised CK-MB1?

Answer 13

Statins (as they can cause myopathy)

Question 14

When does troponin I peak following chest pain?

Answer 14

2-4 hours

Question 15

Within what time period does troponin I return to normal following a cardiac event?

Answer 15

5-10 days

Question 16

What change in troponin levels is indicative of cardiac myocyte injury?

Answer 16

A 50% increase or decrease between 2 measurements