B-QuiCK: Liver function tests (LFTs)

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Liver function tests (LFTs)

Summary: interpreting abnormal LFTs in primary care

Summary: tiered testing recommendations for stable patients with elevated aminotransferase levels (ALT or AST)

Test Abnormality Interpretation or potential cause
First tier
Full blood count (FBC) Macrocytosis* Possibly due to excessive alcohol intake, particularly if GGT also raised
Thrombocytopenia* Portal hypertension (possible hypersplenism) which may also be associated with ultrasound findings of enlarged spleen, portal vein and ascites or varices. Also common in chronic liver disease.
HbA1c or fasting glucose Elevated (e.g. HbA1c > 41 mmol/mol
or fasting glucose > 5.5 mmol/L)
Indicates glucose intolerance conditions, e.g. type 2 diabetes and pre-diabetes; MASLD is common in these patient groups
Lipid profile Abnormal Contributor to fatty liver diseases, i.e. alcohol-related liver disease or MASLD
Iron studies,*
inc. ferritin and TSAT
Elevated Possible haemochromatosis. Check hereditary haemochromatosis (HFE) genotype if repeat testing remains high in fasting and otherwise well patients
Hepatitis screening
(HBsAg and anti-HCVAb)
Positive Suggests hepatitis B or C infection. HCV requires confirmation of infection by either detection of HCV RNA or HCV Antigen
AUDIT-C screening Positive
(score ≥ 3 in female or ≥ 4 in male)
Suggests potential alcohol misuse; full AUDIT tool assessment should then be undertaken
Second tier
Abdominal/ liver ultrasound** Echogenic liver, mass or dilated ducts Can be used to detect fatty liver, malignancy or gall stones/obstruction
Testing for other causes of viral hepatitis, e.g. Hepatitis A, Epstein Barr virus, Cytomegalovirus Positive Suggests infection with corresponding virus; hepatitis A testing may be a first-tier investigation if the patient reports travel to a country where infection is prevalent or contact with local outbreak or MSM
Autoantibodies and Immunoglobulins Antimitochondrial antibody (AMA) positive, increased IgM in combination with cholestatic LFTs Diagnostic of primary biliary cirrhosis
Anti-smooth muscle antibody (SMA)/ anti-liver kidney microsomal (LKM)/anti-liver soluble antigen (SLA)/anti-nuclear antibody (ANA) positive, particularly with elevated IgG Probable autoimmune hepatitis
Coeliac serology screen Positive Suggestive of coeliac disease-related liver damage

Other tests dictated by clinical context or family history of liver disease, such as:

  • Checking alpha-1 antitrypsin levels in people with a family history of deficiency
  • Serum/urine copper and caeruloplasmin testing in patients with a family history of Wilson’s disease

* If these tests have been performed for other clinical reasons and an abnormality is found, then subsequent LFT testing is usually warranted

A fasting sample may improve the accuracy of results if there is uncertainty about an abnormal result

** In patients where ultrasound does not identify any underlying cause and the diagnosis remains uncertain, consider referring for further assessment with FibroScan, if needed (see: “FibroScan is an emerging alternative tool to liver biopsy”). Liver ultrasound is first tier investigation if cholestasis is suspected.

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