Serotonin, 24 Hour, Urine
Use
This test is used for the diagnosis and follow-up of certain carcinoid tumors that produce predominately 5-hydroxytryptophan (5-HTP) but very little serotonin and chromogranin A. It's particularly helpful for a small group of carcinoid tumors that secrete mainly 5-HTP, which may not elevate other markers like serum serotonin or urine 5-hydroxyindoleacetic acid (5-HIAA). The test finds utility in monitoring tumors that exclusively secrete 5-HTP as urine serotonin levels can still be elevated in these cases.
Special Instructions
To avoid interference, patients should not consume foods rich in serotonin or tryptophan such as avocados, bananas, and tomatoes 48 hours before and during specimen collection. Medication adjustments may be required as certain drugs can alter serotonin levels. This test can be ordered electronically or by completing an Oncology Test Request form and sending it with the specimen.
Limitations
Urine serotonin is typically less likely to be elevated in typical carcinoid syndrome. Dietary intake and medication can interfere with results, causing false positives or negatives. Dietary influences are more pronounced in urine serotonin and 5-HIAA levels than in serum serotonin levels. Heavy nicotine use can also falsely elevate urine serotonin measurements due to cross-reactivity with cotinine, a nicotine metabolite. Since the test can be affected by interference, results should be interpreted cautiously in the context of dietary and medication history.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 18253-5
- 18253-5
- 13362-9
- 3167-4
Result Turnaround Time
5-8 days
Related Documents
For more information, please review the documents below
Specimen
Urine
Volume
5 mL
Minimum Volume
2.5 mL
Container
Plastic, 10-mL urine tube
Collection Instructions
Add 25 mL of 50% acetic acid as preservative at start of collection. Collect urine for a full 24 hours and record the total volume. Refrigerate specimen during collection.
Patient Preparation
Avoid certain foods like avocados, bananas, and tomatoes 48 hours before and during collection. Avoid medications that may affect serotonin levels for at least 72 hours before collection. Avoid heavy nicotine consumption during collection period.
Causes for Rejection
Gross hemolysis
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 48 hours |
| Refrigerated | 28 days |
| Frozen | 28 days |