LFTs Flashcards
What are LFTs?
Blood tests to show how well that liver is working
What are the main synthetic functions of the liver?
- Conjugation + elimination of bilirubin
- Synthesis of albumin
- Synthesis of clotting factors
- Gluconeogenesis
What are the 2 main reasons you would order LFTs?
- Confirm suspicion of liver injury
- Distinguish between hepatocellular injury
and cholestasis
What tests are included in LFTs?
ALT -> Alanine transaminase
AST -> Aspartate Aminotransferase
ALP -> alkaline phosphatase
GGT -> Gamma Glutalmyltransferase
Bilirubin
Albumin
Prothrombin time
When are liver enzymes increased?
Chronic high alcohol excess.
Obesity (especially in men).
Smoking (in women).
Drug reaction.
What tests can be used specifically to assess synthetic function in the liver?
Bilirubin
Albumin
Prothrombin time
Blood glucose
When assessing ALP and ALT was is classed X fold increase is classed as ^ and what is classed as ^^.
ALT:
- <x10 = ^
- >x10 = ^^
ALP:
- <x3 = ^
- >x3 = ^^
What do reference ranges for LFTs depend on?
Age
Gender
Health
Ethnicity
How they have been analysed
Units of measurement
What is ALT a marker for and why?
HEPATOCELLULAR DAMAGE
It is usually found in hepatocytes in high concentrations and so when they are damaged ALT enters the blood stream
What does a raised ALT indicate?
Liver cell damage
Liver disease markers of drugs, toxins, viral
What is ALP a marker for and why?
CHOLESTASIS
Concentrated in the liver, bile duct and bones.
Often raised in response to liver pathology b/c raised synthesis in response to cholestasis
Give a ?dDx for the following:
a) >10 ^ in ALT + <3 ^ in ALP
b) <10 ^ in ALT + >3 ^ in ALP
a) ?hepatocellular injury
b)?Cholestasis
Is it possible to have a mixed picture of both hepatocellular injury and cholestasis
Yep
If there is ^ ALP what other liver enzyme do you want to check?
Why?
GGT
^ GGT is suggestive of biliary epithelial damage + bile flow obstruction
What does a markedly increased ALP w/ a raised GGT indicate?
Cholestasis
What else can a ^ GGT indicate?
Liver damage from drugs and alcohol
EG phenytoin
What does an isolated raised ALP indicate?
Bone pathology -> Increased osteoblastic activity
- Paget’s
- Osteomalacia
- Vit D deficiency
- Bony mets from primary bone tumour
- Recent bone #
- Renal osteodystrophy
What could cause of jaundice w/o a ^ in ALP or ALT?
Pre hepatic causes
EG:
- Gilbert’s syndrome (most common)
- Haemolysis
-> check blood film, FBC, reticulocyte
count, hepatoglobin + LDH levels to
confirm
What is bilirubin?
Breakdown product of haemoglobin
When is jaundice usually visible?
usually when >60 umol/L
What is the difference between unconjugated bilirubin and conjugated bilirubin?
Unconjugated is not water soluble so can’t affect urine
Conjugated is water soluble so can make urine darker (in the form of urobilinogen)
How can stools be used to differentiate between the causes of jaundice?
Change in a obstructive picture as bile and pancreatic enzymes are blocked form entering the bowel
Fat isn’t absorbed so stools appear:
- Pale
- Bulky
- Hard to flush
What do the following combos indicate that cause of jaundice being?
a) Normal urine + normal stools
b) Dark urine + normal stools
c) Dark urine + pale stools
a) Pre hepatic
b) Hepatic
c) Post-hepatic (obstructive)
What does a high conjugated bilirubin show?
Liver disease (hepatocellular injury)
Bile duct disease (Cholestasis)
What does a high unconjugated bilirubin show?
Gilbert’s - impaired conjugation
Haemolytic anaemia
Drugs / Congestive HF Impaired hepatic uptake
What is the role of albumin?
Plays a key role in maintaining the oncotic pressure of blood.
Also helps to bind water, cations, fatty acids and bilirubin.
What does a low albumin indicate?
Severe infections -> sepsis
Excessive loss of albumin -> protein losing enteropathies / nephrotic syndromes -> Glomerulonephritis
Chronic inflammatory diseases -> IBD
Hepatitis / cirrhosis -> Liver disease
DM
Trauma / burns
What does a high albumin indicate?
Dehydration / severe dehydration
What does prothrombin time (PT) measure?
The blood’s coagulation tendency, specifically assessing the extrinsic pathway.
What secondary causes can lead to prolonged PT?
Anticoagulant drug use
Vitamin K deficiency
IF there is no known / identifiable secondary cause for prolonged PT what can this indicate?
Why?
Can indicate liver disease and dysfunction.
The liver is responsible for the synthesis of clotting factors, therefore hepatic pathology can impair this process resulting in increased prothrombin time.
What can AST:ALT be used to determine?
Likely cause of liver derangement
-> If it is ACUTE OR CHROINC
What does a AST:ALT ratio of 2:1 indicate?
Associated w/ cirrhosis + acute alcoholic hep (damaged via EtOH)
What does a raised AST indicate?
Alcohol
Liver disease markers of drugs, toxins, viral
What does a AST:ALT ratio of 1:2 indicate?
Associated w/ chronic liver disease
what do globulins measure?
Total proteins
Why do you measure serum blood glucose in LFTs?
The liver plays a significant role in gluconeogenesis
Assessment of serum blood glucose can provide an indirect assessment of the liver’s synthetic function.
Gluconeogenesis tends to be one of the last functions to become impaired in the context of liver failure.
Give the typical LFT pattern in acute hepatocellular damage for the following liver enzymes:
ALT
ALP
GGT
Bilirubin
ALT = ^^
ALP = -/^
GGT = -/^
Bilirubin = ^/^^
What are some common causes of acute hepatocellular damage?
Poisoning
Infection
Liver ischaemia
Paracetamol OD
Hep A/B
Give the typical LFT pattern in chronic hepatocellular damage for the following liver enzymes:
ALT
ALP
GGT
Bilirubin
ALT = -/^
ALP = -/^
GGT = -/^
Bilirubin = -/^
What are some common causes of chronic hepatocellular damage?
Alcoholic fatty liver disease
NAFLD
Chronic infection -> Hep B/C
primary biliary cirrhosis
What are some less common causes of chronic hepatocellular damage?
Alpha-1 antitrypsin deficiency
Wilson’s disease
Haemochromatosis
Give the typical LFT pattern in cholestasis for the following liver enzymes:
ALT
ALP
GGT
Bilirubin
ALT = -/^
ALP = ^^
GGT = ^^
Bilirubin = ^^
Name some conditions that are relevant in a patients?
Gallstones in the past.
Crohn’s/UC.
Surgery in past if malabsorption may have had some bowel removed.
What focused questions would you ask in terms of medications?
Disease control
What meds
How often?
Adherence?
Any other meds
What focused questions would you ask in terms of SHx?
Recent travel anywhere?
Smoking?
Alcohol?
Recreational drugs/toxins? (IVDU?)
Diet.
Impact of condition on life.
Recent tattoos?
In terms of alcohol what questions should you ask?
CAGE questionnaire
And if they are finding it difficult to stop - why?
What advice would you give?
Stop smoking / alcohol / drugs.
Diet advice.
Advice on disease management if they’re non-compliant.
