LFT interpretation

Question 1

Patterns

Answer 1

Acute hepatitis: ALT / AST in 1000s, ALP mildly raised
Chronic hepatitis: ALT / AST in 100s
Obstructive picture: ALP significantly raised, ALT / AST mildly raised, high bilirubin
Alcoholic: raised gamma-GT, high MCV, ALT / AST mildly elevated
Cirrhosis / chronic liver disease: liver enzymes may be normal, low albumin, high coag tests

Question 2

Liver enzymes - leak from damaged liver cells

Answer 2

ALT: specific to liver
AST: liver, heart, skeletal muscle, kidneys, pancreas

Marked increase (>1000) - toxin / drug induced hepatitis, acute viral hep, liver ischaemia
Moderate (300-500) - chronic hep, biliary obs
Mild (< 300) - cirhossis, NAFLD, HCC, HH, wilsons

ALT>AST: chronic liver disease
AST>ALT: established cirrhosis, alcoholic liver disease

Question 3

Alkaline phosphatase (ALP)

Answer 3

Main sources: biliary ducts, bone (paget’s, mets, #, osteomalacia, renal bone disease)

Gamma-GT can help determine in ALP is of hepatic origin 
Marked increase (>4x normal): cholestasis (e.g. gallstones, primary biliary cholangitis, primary sclerosing cholangitis, pancreatic cancer, drugs)
Moderate increase (<3 x normal): hepatitis, cirrhosis, infiltration

Question 4

Gamma - GT

Answer 4

Mirrors ALP so can be used to confirm if a rise in ALP is of hepatic origin
Raised with alcohol abuse and enzyme inducing drugs

Question 5

Bilirubin

Answer 5

Unconjugated hyperbilirubinaemia:
Increased red blood cell breakdown
Impaired hepatic uptake (drugs, HF)
Impaired conjugation (Gilbert’s, physiological neonatal jaundice)

Conjugated hyperbilirubinaemia:
Hepatocellular dysfunction
Impaired hepatic secretion

Question 6

Albumin

Answer 6

Synthesised by the liver and has a half life of around 20 days - changes happen over weeks

Decreased albumin and decreased protein = advanced cirrhosis, alcoholism, protein malnutrition etc
Decreased albumin and normal protein = infection
Decreased albumin and increased protein = myeloma, chronic inflammaiton / autoimmune conditions, acute infection

Question 7

Prothrombin time /INR

Answer 7

Depend on clotting factors and fibrinogen

Raised PT / INR - liver disease, vit K deficiency, consumptive coagulopathy (DIC)

Question 8

Some non hepatic causes of deranged LFTs

Answer 8

Drugs
RHF
Sepsis
Coeliac disease
Haemolysis 
Hyperthyroidism 
RLL pneumonia