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.
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).