5-Hydroxyindole acetic acid (5-HIAA), Random (spot) collection, Urine

Clinical background:

Clinical utility
5-hydroxyindole acetic acid (5-HIAA) is measured in urine for the biochemical diagnosis and monitoring of carcinoid syndrome related to functional gastrointestinal neuroendocrine tumours.

Clinical significance
Gastrointestinal carcinoid tumours can produce excess amounts of serotonin leading to carcinoid syndrome. Serotonin is metabolised to 5-hydroxyindoleacetic acid (5-HIAA), which is excreted in the urine. Significantly elevated urine 5-HIAA levels are almost always associated with carcinoid syndrome, while mildly elevated levels can occur as a result of dietary sources or medications (see below).

Specimen container paediatric:

White universal container

Specimen container adult:

White universal container

Minimum volume paediatric:

1 – 10 mL urine

Minimum volume adult:

1 – 10 mL urine

Special requirements:

Laboratory processing:

Sample stability:

Once pH has been adjusted to 3.0 to 6.0, samples are stable at 4°C for up to 10 days.
For long-term storage, store samples at –20°C.

Transport requirements:

For external laboratories:
Once pH has been adjusted to 3.0 to 6.0, transport urine aliquot at ambient temperature.

Freq Analysis:

1 x weekly

Quality Assurance:

UK NEQAS

Interpretation:

In the presence of carcinoid syndrome, elevated excretion of urine 5-hydroxyindoleacetic acid (5-HIAA) is a probable indicator of the presence of a serotonin-producing tumor, if pharmacological and dietary artifacts have been ruled out.

Reference ranges:

Less than 4.0 µmol/mmol creatinine

Factors affecting result :

Potential causes of false positive results:
Certain foods and medications can cause falsely elevated urine 5-HIAA results, and must be avoided for 48 hours prior to and during urine collection.

Foods to avoid:

• fruits, nuts and vegetables, including avocados, bananas, plums, walnuts, pineapple, aubergine, tomatoes/tomato products, kiwifruit, dates, grapefruit, nuts, cantaloupe/honeydew melon.
• caffeinated food and beverages, including tea, coffee and chocolate.

Drugs/medications to avoid:

• paracetamol, caffeine, diazepam (Valium), nicotine, some cough medicines (containing ephedrine or glyceryl guaiacolate, and phenobarbital.

Potential causes of false negative results:
Certain medications can cause falsely decreased urine 5-HIAA results, and must be avoided for 48 hours prior to and during urine collection.

Drugs/medications to avoid:

• aspirin, ethyl alcohol, imipramine, levodopa, MAO inhibitors, heparin, isoniazid, methyldopa, and tricyclic antidepressants, somatostatin analogues.

Other Info:

Urine 5-HIAA analysis is performed by LC-MS/MS.