Chapter 30 Urine Indican Test (Obermeyer Test)
The essential amino acid tryptophan is converted to indole by intestinal bacterial cleavage of the tryptophan side chain. After absorption, indole is converted to 3-hydroxy indole (indoxyl or indican) in the liver, where it is conjugated with potassium sulfate or glucuronic acid. It is then transported by the blood to the kidneys for excretion. Increased urinary excretion of indican can be an indicator of gastrointestinal bacterial overgrowth and dysbiosis.
Because most of the endogenous indoles have a side chain that prevents cleavage and are instead metabolized to skatole, the production of indicans (indoxyl potassium sulfate and indoxyl glucuronate) reflects bacterial activity in the small and large intestines. Box 30-1 lists conditions in which increased levels are found.1–4 Elevations of indicans are considered an indicator of gastrointestinal dysfunction and overgrowth of anaerobic bacteria (dysbiosis). The indican test can be used to monitor the efficacy of treatment of gastrointestinal dysbiosis.