What are the indications for elevated liver function tests?

Indications for Elevated Liver Function Tests

Elevated liver function tests (LFTs) are not a diagnosis but rather a laboratory finding that requires systematic evaluation to identify the underlying cause, which can range from benign conditions to life-threatening liver disease requiring immediate intervention.

Primary Causes to Evaluate

The evaluation of elevated LFTs should be guided by the pattern of enzyme elevation 1:

Hepatocellular Pattern (Elevated ALT/AST)

When ALT and AST are disproportionately elevated compared to alkaline phosphatase, consider:

• Non-alcoholic fatty liver disease (NAFLD) - Most common cause in patients with metabolic risk factors (obesity, T2DM, dyslipidemia, hypertension) 2
• Alcohol-related liver disease (ARLD) - Screen with AUDIT questionnaire; those drinking >50 units/week (men) or >35 units/week (women) require fibrosis assessment 2
• Viral hepatitis - Test for hepatitis A, B, and C 1
• Autoimmune hepatitis - May present without autoantibodies or elevated immunoglobulins 2
• Drug-induced liver injury - Review all medications including over-the-counter drugs and herbal supplements 3, 1
• Hereditary hemochromatosis - Screen with ferritin and transferrin saturation 3
• Wilson's disease - Particularly in younger patients 1
• Alpha-1 antitrypsin deficiency 1

Cholestatic Pattern (Elevated Alkaline Phosphatase)

When alkaline phosphatase is disproportionately elevated:

• Primary biliary cholangitis 1
• Primary sclerosing cholangitis 1
• Biliary obstruction - Requires imaging evaluation 1

Isolated Hyperbilirubinemia

Elevated total bilirubin should be fractionated into direct and indirect components; elevated conjugated bilirubin suggests hepatocellular disease or biliary obstruction 1, 4.

Critical Risk Stratification

For NAFLD patients, mandatory risk stratification using FIB-4 or NAFLD Fibrosis Score should be first-line testing to determine extent of liver fibrosis 2. Second-line testing requires quantitative assessment with serum ELF or elastography 2.

For harmful drinkers, risk stratification with Fibroscan/ARFI elastography is essential - refer to secondary care if Fibroscan reading is >16 kPa or if there are features of cirrhosis or portal hypertension 2.

Important Clinical Caveats

• Normal LFTs do not exclude advanced fibrosis or cirrhosis 2 - different screening approaches are needed for at-risk populations
• True healthy normal ALT levels are 29-33 IU/L for males and 19-25 IU/L for females 1 - values above this warrant assessment
• Elevated ALT is associated with increased liver-related and all-cause mortality 3, 1
• Obesity and alcohol have synergistic effects - when BMI >35, the risk of liver disease doubles for any given alcohol intake 2
• 25% of patients with metabolic risk factors who drink heavily may still have NAFLD despite alcohol consumption 2

When to Refer

Adults with abnormal liver blood tests, even with negative extended liver etiology screen and no NAFLD risk factors, should be referred to a gastroenterologist/hepatologist for further evaluation 2. This is critical because entirely treatable conditions like autoimmune liver disease may present without typical serologic markers 2.

Refer patients with ARLD and AUDIT score >19 to alcohol services 2.

Initial Workup Requirements

Essential initial testing includes 3:

• Complete blood count
• ALT, AST, alkaline phosphatase, total bilirubin, albumin
• Prothrombin time
• Hepatitis B surface antigen, hepatitis B core antibody, hepatitis C antibody
• Ferritin, iron levels, and transferrin saturation
• Right upper quadrant ultrasound

Liver biopsy may be considered when serologic testing and imaging fail to establish a diagnosis, to stage disease, or when multiple diagnoses are possible 1.