What are the laboratory findings in Gilbert's syndrome (a benign genetic disorder characterized by mildly elevated levels of unconjugated bilirubin)?

From the Guidelines

Gilbert syndrome is diagnosed through blood tests showing elevated unconjugated (indirect) bilirubin levels, with the proportion of conjugated bilirubin being less than 20%-30% of the total bilirubin, as recommended by the most recent guidelines 1. The key laboratory findings for Gilbert syndrome include:

• Elevated total bilirubin levels, typically 1-3 mg/dL
• Low proportion of conjugated bilirubin, less than 20%-30% of the total bilirubin
• Normal liver function tests, including ALT, AST, alkaline phosphatase, and GGT
• Normal complete blood count, ruling out hemolytic anemia Genetic testing for UGT1A1 gene mutations can confirm the diagnosis, but is rarely necessary for clinical management 1. It is essential to distinguish Gilbert syndrome from other causes of hyperbilirubinemia, such as hemolysis or liver disease, to avoid unnecessary diagnostic testing and incorrect assignment of causality 1. The condition results from reduced activity of the enzyme UDP-glucuronosyltransferase, which is responsible for conjugating bilirubin for excretion. No treatment is required for Gilbert syndrome as it's a benign condition, though patients should be aware that certain medications metabolized by the UGT1A1 enzyme may require dose adjustments 1.

From the Research

Gilbert Syndrome Labs

• Hyperbilirubinemia is a condition characterized by elevated serum bilirubin levels, which can be caused by various factors, including disordered bilirubin metabolism or acquired diseases 2
• Diagnosis of Gilbert's syndrome (GS) is typically made when mildly elevated total bilirubin levels are present, along with normal serum activities of liver transaminases, biliary damage markers, and red blood cell counts 2
• Key laboratory findings in GS include:
  • Mildly elevated unconjugated bilirubin levels
  • Normal liver transaminases
  • Normal biliary damage markers
  • Normal red blood cell counts
• These laboratory findings are important in distinguishing GS from other conditions that cause hyperbilirubinemia, such as liver disease or hemolytic anemia 2

Laboratory Testing

• Assessment of bilirubin concentrations is typically conducted as part of routine liver function testing 2
• Bilirubin testing can help identify individuals with GS, who may have a reduced prevalence of chronic diseases, such as cardiovascular disease and type 2 diabetes mellitus 2