How is Gilbert syndrome diagnosed?

Updated: May 21, 2019
  • Author: Hisham Nazer, MBBCh, FRCP, DTM&H; Chief Editor: BS Anand, MD  more...
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As a rule, Gilbert syndrome can be diagnosed by a thorough history and physical examination and confirmed by standard blood tests. Repeated investigations and invasive procedures are not usually justified for establishing a diagnosis.

Hyperbilirubinemia is the only biochemical serum abnormality in Gilbert syndrome. Serum bilirubin concentrations range from 1-5 mg/dL. Two provocative tests, energy deprivation and nicotinic acid administration, have been used to diagnose the condition. However, a significant number of false-positive and false-negative results limit the value of these tests in patients with marginal elevation of serum bilirubin concentration.

A polymerase chain reaction (PCR) assay has also been introduced to identify TA repeats and may be used as a screening test.

A complete blood count (CBC), including a reticulocyte count and a blood smear, is a useful screening test for excluding hemolysis. Rarely, red blood cell abnormalities resembling variegate porphyria, possibly resulting from the increased hepatocellular bilirubin concentration, have been described in persons with Gilbert syndrome.

Serum lactate dehydrogenase (LDH) levels are elevated in persons with hemolysis but are normal in those with Gilbert syndrome.

A familial increase in serum alkaline phosphatase (ALP) levels has been reported in some persons with Gilbert syndrome.

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