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Serotonin, Whole Blood

Test ID: 


CPT code:



•5-HT, Whole Blood

•5-Hydroxytryptamine, Blood

Clinical Use:

Diagnose carcinoid syndrome. The classical syndrome includes flushing and vasomotor instability, diarrhea, hepatomegaly, and endocardial lesions. Ectopic production may occur from oat cell carcinomas of lung, islet cell tumors of pancreas, and medullary carcinoma of the thyroid. Carcinoid tumors occur in multiple endocrine neoplasia, types I and II.

Test Information:

Serotonin is produced by cells of the APUD system, including the enterochromaffin (Kulchitsky) cells distributed through the mucosa of the gastrointestinal tract. Most serotonin in blood is usually concentrated in platelets, which release it during blood coagulation. Serotonin may be measured to confirm the diagnosis of carcinoid syndrome. The carcinoid syndrome is usually caused by primary carcinoids of the ileum, but the syndrome is occasionally caused by primary carcinoids of the stomach. Other organs give rise to carcinoids including pancreas, duodenum, bronchus, and ovary. Most patients with the carcinoid syndrome have hepatic metastases.

Specimen Type:

Whole blood, frozen

Requested Volume: 

10 mL EDTA/ascorbic acid mixture

Container Type: 

Lavender-top (EDTA) tube and transport tube containing 75 mg ascorbic acid.

Patient Preparation: 

Monoamine oxidase inhibitor drugs should be discontinued for at least one week prior to sampling since they tend to increase the level of serotonin.


Sample collection practices that prevent blood clotting and oxidation of serotonin are imperative. Collect three tubes (4 mL each) whole blood. Invert tubes at least ten times to ensure thorough distribution of EDTA. Immediately transfer 10 mL whole blood to transport tube containing 75 mg ascorbic acid. Thoroughly mix by inverting whole blood/ascorbic acid mixture another ten times. Freeze transport tube and send entire collection to the laboratory. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested

Storage Instructions:


Stability Requirements:



Room temperature

3 days


3 days


14 days

Freeze/thaw cycles

Stable x3

Rejection Criteria

Specimen stored without preservative

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