Blood Sciences Test


5-HIAA (Urine)

Specimen

24 hour urine (random urines not suitable)

Special Instructions

Foods high in serotonin content (avocados, bananas, tomatoes, plums, walnuts, pineapples and eggplant) should be avoided for 3 to 4 days  prior to and during the urine collection, otherwise falsely elevated results may be obtained

Units

µmol/24h

Reference Range

< 36.6 µmol/24 h

Test Usage

Measurement of urinary 5-HIAA is useful in the diagnosis and monitoring of patients with the carcinoid syndrome. Symptoms include flushing, diarrhoea, bronchoconstriction, wheezing, right heart valve disease, and fibrosis of the endocardium, blood vessels, and skin. Carcinoid tumors are small slowly growing tumors of enterochromaffin cells. Generally, carcinoid tumors are indolent, but a subset is malignant. Carcinoid syndrome usually occurs following metastases to the liver with subsequent release of hormones directly into the systemic circulation. Approximately 85% of carcinoid tumors are located in the GI tract, 10% in the lung, and 5% in various other sites including thymus, ovary, kidney, prostate, skin, and breast.

Enterochromaffin cells are part of the neuroendocrine system and most of them produce serotonin. Excessive serotonin secretion is responsible for many of the symptoms associated with  carcinoid syndrome. Serotonin is primarily metabolized to 5-HIAA in the liver and kidney. 5-HIAA is water soluble and excreted almost entirely in the urine. Measurement of urinary 5-HIAA is recommended for patients with suspected carcinoid syndrome. More than 90% of patients with carcinoid syndrome have 5-HIAA levels that exceed 75 µmol per 24 hours. If two 24-hour urine collections during spells fail to reveal an increased 5-HIAA level, the diagnosis of a functioning carcinoid tumour is unlikely.

Availability

Local test

Turnaround Time

1 week

Cannot be added on to an existing request

Specimen Labelling Procedure