Analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS)
Clinical details: 
5-Hydroxy-indole-acetic acid (5-HIAA) is the metabolite of 5-hydroxytryptamine (serotonin). Serotonin is produced by the argentaffin cells of the GI tract. Serotonin is over-produced in the carcinoid tumours of the GI tract. These are associated with flushing attacks, diarrhoea and abdominal pain. Most carcinoid tumours are metastatic to the liver at the time of detection. Resection of the primary tumour, partial hepatectomy and embolization are the primary forms of treatment, although radiolabelled octreotide has been used more recently. 5-HIAA is invariably increased in classical carcinoid, although some tumours may be non-secretory. 5-HIAA is also increased with high dietary serotonin intake or other GI tract disease e.g. coeliac disease.
Reference range: 

< 42 umol/24h or <4.0 umol/mmol creat

umol/24h (timed) or umol/mmol creat (random)
Sample type and Volume required: 
Timed (24h) urine collections are preferred for investigations of adults for carcinoid syndrome. Samples should be collected into containers with an anti-bacterial agent (boric acid) or into acid containing bottles. Acidification of the sample prior to despatch provides greater stability for the analytes measured. A 10-25 mL aliquot is preferred with the 24h urine volume provided. Random samples can be used in adults.
Turnaround time: 
7 working days
Patient instructions: 

Pre-sample preparation is important for accurate 5HIAA test results. Food staff rich in serotonin should be avoided for 48hr prior to and during urine collection. These include avocados, bananas, pineapples, plums, walnuts, tomatoes, kiwi fruit, sweetcorn, broccoli, spinach and eggplant. There are also certain cough medicine that contain serotonin that can affect the 5HIAA test  

Storage and transport: 
Send by overnight first class post.
Reference Biochemistry Department at King's College Hospital
020 3299 4107
King's College Hospital
Denmark Hill
London SE5 9RS
Metabolic Laboratory at King's College Hospital
020 3299 4128
King's College Hospital
Denmark Hill
London SE5 9RS
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 03/07/2023