Liver function tests

What kind of liver abnormality does the patient have:

• Isolated bilirubin?

• Cholestatic?

• Hepatitic?

1. Isolated raised bilirubin: Most commonly caused by Gilbert’s syndrome (affects 8% of the population); consider haemolysis in patients with anaemia.
2. Cholestatic: Predominantly raised ALP (alkaline phosphatase) and GGT (gamma glutamyltransferase) indicate cholestasis. Common causes include: primary biliary cirrhosis, primary sclerosing cholangitis, biliary obstruction (stones, strictures, neoplasia etc), and drug induced liver injury
3. Hepatitic: Predominantly raised ALT (alanine transaminase) and AST (aspartate aminotransferase) indicate hepatocellular liver injury (hepatitis). Common causes include: viral hepatitis, non-alcoholic fatty liver disease (NAFLD), alcohol related liver disease (ARLD), autoimmune hepatitis, and drug induced liver injury.

 Elevated GGT?

Alcohol consumption, drug induced liver injury, NAFLD, cholestatic liver disorders, liver metastases, hepatic congestion secondary to heart failure.

 ELEVATED GGT and ALP?

Elevated GGT and alkaline phosphatase (ALP) with normal or less pronounced elevations of ALT or AST is suggestive of a cholestatic disorders: gallstones, pancreatic cancer, cholangiocarcinoma, primary biliary cirrhosis, primary sclerosing cholangitis, or drug induced liver injury.

The description of pale stools, dark urine, and itching is characteristic of post hepatic jaundice.

ELEVATED TRANSAMINASE?

In alcohol related disease, AST tends to rise higher than the ALT. In alcoholic hepatitis and cirrhosis, the AST/ALT ratio is greater than 2 in around 70% of patients.
In alcoholic hepatitis, serum AST levels rarely rise above 500 iu/L and ALT rarely rises above 300 iu/L. In comparison, acute infectious hepatitis and drug and toxin injury often cause much higher ALT and AST rises.

In patients with NAFLD (non-alcoholic fatty liver disease), the typical abnormality is mildly raised serum ALT and/or GGT levels.

ELEVATED FERRITIN AND LIVER DISFUNCTION?

Raised ferritin with normal saturation < 45 % and a raised corpuscular volume (MCV) is suggestive of ARLD.

Hepatic function	Clinical feature in acute liver failure
Bilirubin metabolism	Jaundice
Gluconeogenesis	Hypoglycaemia
Ammonia clearance	Hepatic encephalopathy/cerebral oedema
Lactate clearance	Lactic acidosis
Protein synthesis	Coagulopathy
	Neutrophil dysfunction, risk of sepsis
	Ascites

Resources:

• http://learning.bmj.com/learning/modules/flow/JIT.html?execution=e1s3&moduleId=10054395&status=LIVE&action=start&_flowId=JIT&sessionTimeoutInMin=90&locale=en_GB&shouldStartAtQuestionSection=false&page=2
• Giannini EG, Testa R, Savarino V. Liver enzyme alteration: a guide for nclinicians. CMAJ 2005;172(3):367-79.
• Jonston DE, Special considerations in interpreting liver function tests, Am Fam Physicians 1999; 59(8), 2223-30