Diagnostic Tests for Carcinoid Syndrome

Diagnostic tests for carcinoid syndrome

Carcinoid syndrome is usually a manifestation of metastatic carcinoid tumor. This is because the liver acts as a first filter metabolizing hormones secreted by the carcinoid tumor draining into the portal circulation. An exception would be ovarian carcinoid which can drain into the systemic circulation.

Biochemical markers of carcinoid syndrome

5-Hydroxy Indole Acetic Acid

5-HIAA is the metabolite of serotonin released from the carcinoid tumor. 24 hour urinary 5-HIAA estimation has about 73% sensitivity and nearly 100% specificity for diagnosis of carcinoid syndrome [1, 2].

Chromogranin A

Chromogranin A is seen in the synaptic vesicles storing serotonin and levels indicate the bulk of the carcinoid tumor. CgA estimation has around 63% sensitivity and 98% specificity for diagnosis of carcinoid syndrome.

Imaging studies

¹¹¹In-pentetreotide scanning is useful in locating the carcinoid tumor. ¹²³I-MIBG is another radio labelled scan for carcinoid tumors, though less specific. Magnetic resonance imaging, computed tomography and positron emission tomography are other important modalities useful in assessing the size of the tumor.

References

1. J M Feldman, T M O’Dorisio. Role of Neuropeptides and Serotonin in the Diagnosis of Carcinoid Tumors. Am J Med. 1986 Dec 22;81(6B):41-8.
2. J Maroun, W Kocha, L Kvols, G Bjarnason, E Chen, C Germond, S Hanna, P Poitras, D Rayson, R Reid, J Rivera, A Roy, A Shah, L Sideris, L Siu, R Wong. Guidelines for the Diagnosis and Management of Carcinoid Tumours. Part 1: The Gastrointestinal Tract. A Statement From a Canadian National Carcinoid Expert Group. Curr Oncol. 2006 Apr;13(2):67-76.