Chemical Pathology 15 - Enzymes and cardiac markers Flashcards
What is the Km?
Michaelis Mentin constant
= concentration of substrate at which the reaction velocity is 50% of maximum
What tumour marker can be used for germ cell, ovarian and testicular malignancies?
AFP
When is ALP elevated physiologically?
In pregnancy and childhood
Recall 4 pathologies that can cause a raised ALP
How to distinguish between the diff sources of ALP?
- Bile duct pathology (eg cholestatic liver disease)
- Bone pathology (fracture/ metabolic bone disease)
- Germ cell tumours
- Intestinal pathology (but not routinely used for investigation of bowel disorders)
*To distinguish between the diff sources: can order bone specific ALP assay; OR can order gamma GT- which would rise in the case of liver source of ALP*
Which LFT enzyme is most specific to liver pathology?
ALT
How can hepatic and biliary disease be best distinguished on the LFTs?
ALT:ALP ratio
If ALT much higher than ALP = hepatic
How many isoenzymes of LDH exist?
5
Recall 3 things that a raised LDH may indicate
- Haemolytic anaemia
- Tumour marker (lymphoma, germ cell testicular Ca)
- Myositis (rheum)
Which enzyme is markedly raised in acute pancreatitis?
Serum amylase
What is the most likely cause of a raised CK-MB1?
Rhabdomyolysis (history of long lie/ big fall?)
Where is CK-MB1 vs CK-MB2 produced?
CK-MB1 - skeletal muscle
CK-MB2 - cardiac muscle
**you only have one heart but several muscles - but it’s actually the opposite of this!
In which population is CK physiologically slightly raised?
Afrocaribbean
Which prescription drug may be the cause of a raised CK-MB1?
Statins (as they can cause myopathy)
When does troponin I peak following chest pain?
2-4 hours
Within what time period does troponin I return to normal following a cardiac event?
5-10 days
**this means it is not a good marker of re-infarction
What change in troponin levels is indicative of cardiac myocyte injury?
A 50% increase or decrease between 2 measurements
When is amylase level high?
Usually after acute pancreatitis
*usually 10x the upper limit of normal*
What other nonspecific conditions can cause a ise in amylase?
renal insufficiency
intestinal infract/peirtonitis
cholecytsitis
salpingitis
ectopic pregnancy
What does lipase >3 upper reference range indicate?
acute pancreatitis
Which is the most specific marker of acute pancreatitis?
Serum LIPASE
What is creatine kinase a marker of?
Muscle damage
What are the two types of creatine kinase?
CK-MM: skeletal muscle
CK-MB (1 and 2): cardiac muscle
What causes high creatine kinase?
Physiological: Afro-Caribbean (<5x upper limit of normal)
• Pathological: Duchenne Muscular Dystrophy (>10xULN), MI (>10xULN), Rhabdomyolysis,
Statin related myopathy (spectrum of myalgia to rhabdomyolysis occurring secondary to taking statins. RF: high dose, genetic predisposition, previous history of myopathy with another statin. Causes rise in CK. Reversible with cessation of statin).
What is BNP?
What is a more sensitive marker than BNP?
NT-proBNP
What isoform of troponin is a marker of cardiac injury?
Troponin I/T
When do you measure troponin following an MI?
At 6 hours and 12 hours opst onset of the pain
*100% sensitive and 98% specific at 12-24 hours*
How long does troponin remain elevated for?
3-10 days
When else can troponin be raised?
Coronary spasm
Coronary dissection
PCI
myocarditis
HF
cardiomyopathies
Sepsis
Cardiac surgery
Chest trauma
Defibrillation
What is an international unit?
In chemical pathology, the term “international unit” or IU is used to show the concentration of an enzyme e.g. the upper limit of normal for ALT is 40IU/litre.
Put simply: 1 international unit is the quantity of enzyme that catalyses 1uMol of substrate in a minute (at a given temp and pH)
It is a measure of enzyme activity not mass or concentration
How to measure re-infarction?
measure CK-MB
*better than troponin I because troponin I stays elevated for 10 days following an acute event*
Troponin I vs T
Troponin I is more specific and sensitive
**I am the best**
