Imperial Collage Healthcare

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Test Background
5-HIAA is a metabolite of the 5-hydroxytryptamine (5-HT) neurotransmitter (also known as serotonin). Increased 5­HT turnover is characteristic of carcinoid syndrome. Tumours may occur anywhere in the GI tract and can typically secrete 5 HT, catecholamines, prostaglandins and histamine.

Clinical Indications
Carcinoid syndrome, characterised by symptoms of flushing and diarrhoea. Abdominal pain, bronchial asthma, heart failure and pellagra may also be present.

Reference Range
<40 μmol/24 h

Sample Required
24 hour urine collection acidified

Sample Volume
24 hour urine collection


Stable at 2-8oC however freezing pending dispatch recommended.

Sample can be sent by first class post.

Turnaround Time
2 weeks


Certain foodstuffs may cause false positive results. These include: avocados, bananas, plums, walnuts, pineapples, tomatoes, aubergines and cough mixtures containing glycerol guaiacolate. The patient must follow the specified diet for 72hrs with the urine being collected in the last 24hrs (patient diet sheet for 5HIAA collection is provided together with the acidified container).

Samples with pH>5.0 are unsuitable for this assay.

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