Liver Function Tests (LFT)

Last updated 20.09.12

 

Index

 

Features

- Serum based assessment of liver function

- Commonly used in comjunction w other tests to assess liver synthetic function & damage

- Two main patterns: hepatitic & cholestatic

 

Tests

- ALT

- AST

- ALP

- GGT

 

Procedure

-  Venepuncture: orange tube

 

Tests

- Intrahepatic transferases: ALT, AST

-  Elevated in liver injury (hepatitic)

- Biliary tree enzymes: ALP, GGT

-  Elevated in cholestasis

- Typical accompanying tests

-  Bilirubin (total, direct), INR, albumin, total protein

-  For full liver examination + platelets, BSL

 

Uses

- Assess function of liver & possible aetiology

- Ix of jaundice

- Assessment of chronic liver disease

 

Interpretation

- Hepatitic picture

-  High ALT & AST

-  Upto 1.5x normal may not = disease

-  AST > ALT (> 2:1): EtOH hepatitis

-  ALT > 500 unlikely just EtOH

-  ALT > AST: viral hepatitis

- Cholestatic picture

-  High ALP, GGT & Bilirubin

-  Intrahepatic: drug induced

-  Extrahepatic: biliary obstruction

-  Cholestatic non-jaundice picture

-  High ALP & GGT w normal Bilirubin

-  Abscess, metastasis

-  Isolated rise in ALP: bone growth or injury, PBC, pregnancy

-  Isolated rise in GGT: EtOH, drugs

 

 

 

ALT (Alanine Amino Transferase)

<LFT>

 

 

- Most sensitive marker for liver disease

- Specific for liver but also found in kidney, heart & muscle

- Related to BMI of person

- Elevations

-  Very high

-  Acute liver damage (viral hepatitis..), hepatotoxic drugs, lead poisoning, shock, necrosis of large tumour

-  Moderate

-  EtOH abuse, CMV, EBV, hepatotoxic drugs, rapid growth in young children

-  Slight

-  Severe burns, obesity, cirrhosis, vigorous exercise, HCC, intramuscular infections, kidney damage, AMI, pancreatic injury, polymyositis, thyroid disease, normal

-  Chronic

-  Alpha-1 antitrypsin def., coeliac disease, haemochromatosis, Wilsons disease

- Decreases

-  Vit B12 deficiency, cyclosporine, interferon

 

 

 

AST (Aspartate Amino Transferase)

<LFT>

 

- Less specific for liver disease than ALT

- Found in liver, heart, muscle, kidneys, pancreas, RBCs

- More sensitive but less specific than ALT for acute liver injury

- Elevations

-  Acute

-  Liver disease

-   Hepatitis, cholestasis, EtOH, hepatotoxicity, abscess, carcinoma

-  Heart disorders

-   AMI, myocarditis, arythmias, CCF, pericarditis, PCI

-  Skeletal m. conditions

-   Strenuous exercise, IM injections, Sx, muscular dystrophy, trauma

-  Haemolytic or Megaloblastic anaemia

-  Pancreatitis, PE, ARF, severe burns, stroke, DTs..

-  Chronic

-  Liver disease

-   EtOH, alpha-1 antitrypsin def, hepatitis, drugs, fatty liver, haemochromatosis, Wilsons disease

-  Muscle diseases, coeliac disease, strenuous exercise

 

 

 

ALP (Alkaline Phosphatase)

<LFT>

 

- Biliary tree membrane bound enzyme

- Isoenxymes found in bone, placenta & liver (bile ducts)

- Should use fasted samples, do not freeze

- Elevation

-  < 3x normal = nonspecific

-  Liver disease

-  Fatty meal (2 hrs), cholestasis, acute fatty liver, amyloidosis, biliary atresia, cirrhosis, CMV, liver metastasis, EBV, hepatitis, PSC..

-  Bone

-  Acromegaly, bone growth, healing fracture, leukaemia, myelofibrosis, osteosarcoma, Pagets disease, Rickets, osteomalacia, 2o hyperparathyroidism

-  Atherosclerosis, CCF, DM, PE, Fanconis syndrome, Hodgkins disease, PUD, pneumonia, pregnancy, drugs..

- Decreased

-  Hypophosphataemia, HIV-1 infection, hypothyroidism, milk alkali syndrome

-  Marked decrease in pregnancy: placental insufficiency, imminent foetal death

 

 

 

GGT (Gamma Glutamic Transpeptidase)

<LFT>

 

- Biliary tree membrane bound enzyme

- Found in liver, kidneys, pancreas, lymphocytes, brain & testes

- Sensitive indicator of biliary outflow obstruction

- Assess recent EtOH intake

- Helps determine hepatobiliary cause of elevation of ALP

- Can be used as an indicator for prostatic Ca or hepatic mets from breast & colon

- High presence of GGT in ascitic fluid indicates hepatoma rather than cirrhosis or liver mets

- Elevation

-  Liver disease: cholestasis, EtOH liver disease, cirrhosis, hepatitis, EBV, liver mets or Ca

-  Panreatic disease, DM, AMI, CCF, trauma, CRF, COPD, malignancies, SLE, sepsis, pregnancy, hypothyroidism, drugs

-  Decreased

-  Hypothyroidism, GGT def. (familial), drugs