Additional Testing Requirements

First-line testing for the diagnosis of carcinoid tumors with symptoms suggestive of carcinoid syndrome consists of urinary 5-HIAA (HIAA / 5-Hydroxyindoleacetic Acid, 24 Hour, Urine), and serum chromogranin A (CGAK / Chromogranin A, Serum). Serotonin in whole blood (SERWB / Serotonin, Blood), serum (SER / Serotonin, Serum), and urine (SERU / Serotonin, 24 Hour, Urine) are useful in conjunction with these first-line tests.

Specimen Required

Patient Preparation: Patient should not take medications that may elevate serotonin levels, including lithium, monoamine oxidase inhibitors, methyldopa, morphine, and reserpine, or selective serotonin reuptake inhibitors (SSRI, eg, PROZAC) which can lead to depletion of platelet serotonin levels and result in false-negative serotonin results for a minimum of 72 hours before specimen collection. Some drugs with longer half-lives (i.e. fluoxetine) can require months after discontinuation for serotonin levels to return to baseline.

Supplies: Serotonin Tube (T259)

Collection Container/Tube: Lavender top (EDTA)

Submission Container/Tube: Serotonin tube containing ascorbic acid

Specimen Volume: 2.5 mL

Collection Instructions:

1. Immediately after collection, transfer approximately 2.5 mL of whole blood to the serotonin tube and mix well (any volume of whole blood from 1.5-3 mL is acceptable).

2. Immediately freeze specimen (necessary to lyse the red blood cells).