Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
Intestinal carcinoid tumours along with neuroendocrine tumours can produce excess amounts of serotonin (5-hydroxytryptamine, 5-HT), which is a vasoactive, powerful smooth muscle stimulant. Serotonin is metabolised to 5-hydroxyindoleacetic acid (5-HIAA) and excreted into urine. Elevated 5-HIAA levels are almost always associated with carcinoid syndrome while mildly elevated levels can occur in non-tropical sprue or from a dietary source such as walnuts, bananas and other serotonin containing fruits.
Specimen container paediatric:
Random urine collection: white universal container [Send to laboratory immediately].
Specimen container adult:
24 urine collection: a 24 hour urine collected into a container with sand and sulphuric acid preservative.
Overnight urine collection: an overnight urine collection into a container with sand and sulphuric acid preservative.
Random urine collection: white universal container [Send to laboratory immediately].
Minimum volume paediatric:
1 – 10 mL urine
Minimum volume adult:
1 – 10 mL urine
Special requirements:
Screening: Overnight urine with sand/sulphuric acid preservative. Random urine acceptable if sent to lab immediately.
Diagnosis and monitoring of known carcinoid: 24h urine with sand/sulphuric acid preservative.
Sample stability:
Once pH has been adjusted to 3.0-3.5, samples are stable at 4°C for up to 10 days.
For long-term storage, store samples at –20°C.
Transport requirements:
Ambient temperature.
Interpretation:
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.
Intake of food with a high content of serotonin (avocados, bananas, plums, walnuts, pineapple, aubergine, tomatoes/tomato products, kiwifruit, dates, grapefruit, nuts, cantaloupe/honeydew melon) within 48 hours of the urine collection could result in falsely elevated 5-HIAA excretion.
Numerous drugs affect the excretion of 5-HIAA by different mechanisms, including increased serotonin synthesis, metabolism, and release and inhibition of uptake.
Reference ranges:
24-hour urine collection:
Less than 40 µmol/24h
Random (and overnight) urine collection:
Less than 4.0 µmol/mmol creatinine
Factors affecting result :
Intake of food with a high content of serotonin (avocados, bananas, plums, walnuts, pineapple, aubergine, tomatoes/tomato products, kiwifruit, dates, grapefruit, nuts, cantaloupe/honeydew melon) within 48 hours of the urine collection could result in falsely elevated 5-HIAA excretion.
Drugs that can increase 5-HIAA secretion include paracetamol, caffeine, diazepam (Valium), nicotine, some cough medicines (containing ephedrine or glyceryl guaiacolate, and phenobarbital. Drugs hat can decrease 5-HIAA include aspirin, ethyl alcohol, imipramine, levodopa, MAO inhibitors, heparin, isoniazid, methyldopa, and tricyclic antidepressants. If possible, following discussion with a doctor, potential interfering drugs should be discontiued at least 48-hours prior to and during urine collection.