Are there any specific laboratory tests that can help confirm a diagnosis of Gilbert's Syndrome?

Specific laboratory tests to confirm Gilbert's syndrome primarily involve measuring serum bilirubin levels, particularly unconjugated hyperbilirubinaemia, in the absence of other liver function abnormalities. Gilbert's syndrome is characterized by a mild, intermittent increase in unconjugated bilirubin without evidence of hemolysis or liver disease ¹.

There is no single definitive diagnostic test; rather, the diagnosis is clinical and biochemical, supported by exclusion of other causes of jaundice. Typically, isolated mild unconjugated hyperbilirubinaemia is found on blood tests, with normal liver enzymes and no signs of hemolysis ¹.

Genetic testing for mutations in the UGT1A1 gene, which encodes the enzyme UDP-glucuronyl transferase responsible for bilirubin conjugation, can support the diagnosis but is not routinely required in clinical practice ¹; (Wagner et al., 2018).

Other laboratory tests may be performed to exclude alternative diagnoses, such as full blood count, liver function tests, and hemolysis screen, but these are to rule out other causes rather than confirm Gilbert's syndrome itself ¹.

In summary, the key laboratory finding suggestive of Gilbert's syndrome is isolated unconjugated hyperbilirubinaemia with normal liver function tests and no evidence of hemolysis, supported by clinical context and exclusion of other causes ¹; (Faragó and Melegh, 2008).