How do you screen for carcinoid syndrome?

From the Guidelines

To screen for carcinoid syndrome, the initial test of choice is a 24-hour urine collection for 5-hydroxyindoleacetic acid (5-HIAA), which measures the main metabolite of serotonin, as recommended by the most recent guidelines 1. This approach is crucial because carcinoid syndrome typically occurs when a neuroendocrine tumor has metastasized to the liver, allowing vasoactive substances to enter systemic circulation without being metabolized by the liver first. Some key points to consider when screening for carcinoid syndrome include:

• Biochemical evaluation, particularly in patients with symptoms suggestive of hormone hypersecretion, using a 24-hour urine collection for 5-HIAA 1
• Imaging studies, such as CT or MRI scans, to locate the primary tumor and any metastases, with multiphase CT or MRI scans recommended for evaluation of liver metastasis 1
• Radiolabeled somatostatin receptor scintigraphy, performed using the radiolabeled somatostatin analogue [111In-DTPA]-octreotide, may also be used in the initial evaluation of patients with NETs 1
• Endoscopic procedures, such as colonoscopy, small bowel imaging, endoscopic ultrasound (EUS), and/or esophagogastroduodenoscopy (EGD), may be necessary depending on suspected tumor location 1 Early detection is crucial as it allows for more effective management of symptoms like flushing, diarrhea, and heart valve damage through treatments such as somatostatin analogs (octreotide, lanreotide) and tumor-directed therapies. It's worth noting that while other studies, such as 1, 1, and 1, provide additional information on the diagnosis and management of neuroendocrine tumors, the most recent and highest quality study 1 should be prioritized when making a definitive recommendation.

From the Research

Screening for Carcinoid Syndrome

To screen for carcinoid syndrome, several methods can be employed, including:

• Measuring plasma 5-hydroxyindoleacetic acid (5-HIAA) levels, which has been shown to be a useful marker for monitoring carcinoid disease 2
• Assessing whole blood serotonin levels, although this may have limitations due to variability in platelet count 2
• Evaluating urinary excretion of 5-HIAA, which is a specific marker for the carcinoid syndrome 3
• Using serum chromogranin A as a nonspecific biochemical tumor marker for carcinoid tumors 3
• Conducting localizing studies such as transabdominal ultrasonography, endoscopy, and computerized tomography to identify the primary tumor site 3

Biomarkers for Carcinoid Heart Disease

In addition to screening for carcinoid syndrome, biomarkers can also be used to detect carcinoid heart disease (CHD), including:

• Serum 5-HIAA (s5HIAA), which has been shown to be a good biomarker for CHD detection 4
• Urinary 5-HIAA (u5HIAA), which is correlated with s5HIAA and can be used to detect CHD 4
• NT-proBNP, which may also be useful in detecting CHD, although its performance is not as well-established as s5HIAA 4
• Higher 5-HIAA levels, which have been found to correlate with disease progression and increased risk of mortality in patients with CHD 5

Diagnostic Approaches

A combination of clinical evaluation, biochemical markers, and imaging studies can be used to diagnose carcinoid syndrome and CHD, including:

• Clinical presentation, such as cutaneous flushing and diarrhea 3
• Biochemical markers, such as 5-HIAA and chromogranin A 2, 3
• Imaging studies, such as echocardiography and computerized tomography 3, 4
• Localizing studies to identify the primary tumor site 3