Module 3 - Hepatic & Lipid Tests Flashcards
What are some functions of the liver?
- cholesterol synthesis and excretion
- removal of old RBCs
- activation of vitamin D
- detoxification and metabolism
- synthesis of proteins and clotting factors (albumin, INR)
- processes nutrients
- storage (glycogen, fats, iron, copper, vitamins)
What are considered “synthesis tests”?
- INR
- albumin
What are considered “cholestatic tests”?
- ALP
- GGT
- Bilirubin (conjugated)
What are considered “hepatocellular damage tests”?
- AST/ALT
- LDH
- Bilirubin (total)
What are LFTs?
liver function tests
*not really accurate since many of the tests included in a LFT panel don’t measure function, they measure damage
_____ is responsible for producing clotting factors
Liver
*If liver is substantially diseased (>80% loss of function) clotting factors are dysfunctional or l=not produced
Abnormal clotting factors = _______ INR
increased
What things can increase INR?
- warfarin
- antibiotics (decreased vitamin K production in gut)
- malabsorption of vitamin K
- genetic clotting factor deficiencies
______ is a protein synthesized from amino acids in the liver
Albumin
What is albumin important for?
- maintaining osmotic pressure in the blood (albumin expands blood volume)
- transport of hormones, drugs, fatty acids and ions
Half life of albumin?
Long half-life (20 days)
Possible reasons for albumin to be low?
- malnutrition
- loss in the urine (kidney disease)
- severe burns
- large amounts of fluid administration (dilution)
- pregnancy (dilution)
Bilirubin metabolism:
Starts off with ?
Breakdown of RBCs
Bilirubin metabolism:
Hemoglobin converted to bilirubin in _____
spleen
Bilirubin metabolism:
Liver makes bilirubin ______ ______
water soluble (direct or conjugated bilirubin)
Bilirubin metabolism:
_____ bilirubin is excreted into the bile
Conjugated
Bilirubin metabolism:
Conjugated bilirubin ends up in the ______ to be excreted in stool (brown color)
intestines
Bilirubin metabolism:
If there is a blockage in the bile duct (cholestastis), conjugated bilirubin can be found in the _____
urine
Direct bilirubin = ______
soluble (in water)
Indirect bilirubin = _______
insoluble
Should direct/conjugated bilirubin be in the blood?
NO WAY
What does an elevated direct bilirubin level indicate?
that something is preventing bile flow to the intestines
**liver is working (conjugating) but it can’t get rid of the water-soluble bilirubin due to obstruction or damaged liver cells
What are potential causes of having increased levels of direct bilirubin?
- obstruction of the bile duct
- intrahepatic cholestasis
- hepatitis
- toxins
- cirrhosis
What is ALP?
Alkaline Phosphatase (ALP) -A group of isoenzymes that remove phosphate groups from molecules (exact function of these isoenzymes still being discovered)
ALP:
____% in liver and bone
80
ALP:
___% in the intestine
20
What types of people may have an elevated ALP?
- children and adolescents have higher ALP due to bone development
- pregnancy (placental ALP)
- elevated in bone disorders (i.e. fractures, cancers)
ALP is also elevated in pts with _______ disease
cholestatic
*bile accumulation = increased ALP synthesis
How long does it take for ALP to be elevated in patients with cholestatic disease?
4-6 weeks for elevation to occur (SLOW)
Once obstruction is resolved, ALP returns to normal in _____ weeks
2-4
Since ALP is a non-specific test, what do you need to interpret it with?
GGT
What is GGT?
Gamma-Glutamyl Transferase
-enzyme that carries gamm-glutamyl functional groups
GGT is ______ for cholestatic disorders but not ______.
it is sensitive but not specific
good for ruling out cholestasis but not good for ruling it in
GGT may be elevated after an _____ ______
myocardial infarction
GGT is strongly associated with ?
alcoholic liver disease
GGT/ALP ratio > 2.5 is indicative of what?
ethanol abuse
Abstinence from alcohol can reduce GGT by ___% in 2 weeks
50
List a few drugs that can cause cholestasis
- NSAIDs
- oral contraceptives
- B-lactams
- amiodarone
- more on slide 16
ALT converts what?
alanine to glutamate
AST converts what?
aspartate to glutamate
Describe AST
Aspartate Transaminase (AST):
- found in liver as well as heart, skeletal muscle, kidneys, brain, pancreas, spleen, lungs and RBCs
- less specific to the liver than ALT
- half life of 17 hours
Describe ALT
Alanine Transaminase:
- More specific to the liver than AST (but can still be found in other tissues such as kidneys, heart, muscle and pancreas)
- Half life of 47 hours
AST & ALT are generally higher in the _______
afternoon
Vigorous exercise can ______ AST/ALT (muscle breakdown)
increase
Dialysis can _____ AST/ALT levels
decrease
Transaminase levels don’t correlate with disease _______
severity
Most of bilirubin is ______
unconjugated
Why might total bilirubin be elevated in hepatocellular injury?
hepatocyte damage = decreased bile production/flow
Symptoms of hyperbilirubinemia?
- jaundice
- pruritus
- xanthomas (lipid deposits in skin)
In premature babies, high bilirubin can cause _____
kernicterus
What is kernicterus ?
rapid RBC breakdown - BBB not formed + liver enzymes not formed = bilirubin buildup in the brain = DAMAGE
What is LDH?
Lactate dehydrogenase:
-an enzyme responsible for converting lactate to pyruvate (and vice versa) in anaerobic metabolism
Why is LDH not really that clinically useful?
it is non-specific to the liver
What may LDH be helpful in differentiating?
Causes of acute liver injury
ALT/LDH ratio > 1.5 = ?
viral hepatitis
ALT/LDH ratio < 1.5 = ?
ischemic hepatitis or acetaminophen toxicity
What are some signs and symptoms of hepatic injury/disease?
- right upper quadrant pain
- jaundice
- pruritus
- ascites (fluid accumulation in peritoneal cavity)
- malaise/fatigue
- malnutrition/anorexia/muscle wasting
What test results would indicate cholestasis?
increased ALP AND increased GGT AND increased conjugated bilirubin
What test results would indicate hepatoceullar injury?
increased AST/ALT AND/OR increased bilirubin AND/OR increased LDH
What does idiosyncratic mean?
not dose-related
What are examples of idiosyncratic causes (not dose-related)?
Allergic reaction
Bile duct injury
Hepatocellular injury
What are examples of drugs that can cause dose-related hepatotoxicity?
- TYLENOL MAN
- Also cocaine and meth
LDL = _____
bad
HDL = _____
good
LDL formula
LDL = total cholesterol - HDL - (TGs/2.2)
If TGs are too high (> 4.5 mmol/L) LDL is _____
inaccurate
What does HDL do?
scavenges cholesterol out of vessels and tissues
After eating, TGs appear in plasma ____ hrs after a meal and peak in _____ hours and can persist for up to 14 hours
2 hrs
4-6 hrs
What type of patients have high TGs?
- diabetes
- kidney disease
- obesity
- liver disease/alcoholism
What type of medications can increase TG and LDL levels?
steroids, antipsychotics, thiazide diuretics
For most patients, LDL target is ??
50% reduction or < 2 mmol/L
What is CK?
Creatine Kinase:
-enzyme that stimulates transfer of high-energy phosphate groups
CK can be used as a marker for what?
muscle injury/death (MI, myopathies)
What type of people can have elevated CK?
marathon runners or people who do intense physical activity
What is a myopathy?
A general term referring to any muscle disease
*CK levels N/A
What is myalgia?
Muscle pain or weakness
*CK levels normal
What is myositis?
A myalgia with increased CK levels
*Increased but <10x ULN
What is rhabdomyolysis?
Muscle symptoms with marked CK elevation and renal symptoms (creatinine elevation)
*CK levels > 10-25x ULN with renal symptoms
When should CK decline if you stop a statin and that was the cause of the muscle pain?
in 3-4 days
What lipid ab tests do you order when a pt is on statin?
**THIS IS DIFFERENT FROM WHAT WE LEARNED IN CLINICAL
TC, LDL, HDL, TC/HDL, TG
When do you order these lipid lab tests when on a statin?
Baseline, 6-8 weeks after initiation, then every 6 months
What lab tests do you order for liver injury?
AST/ALT
When do you order liver injury lab tests?
Baseline, then only if symptoms are present
If AST/ALT > ____ ULN consider stopping statin
3x
What lab tests do you order for muscle injury when on statin?
CK
When do you order muscle injury lab tests?
Baseline, then only if symptoms present
If CK > ____ ULN then STOP statin. When resolved, decrease dose or switch statin
10x
If CK < 10x ULN, what do you do?
continue but lower statin dose