Tumor marker tests

Blood samples may be collected for a range of tests. Markers for NETs that may be measured in the blood include:

• Chromogranin A (CgA) is one of the most common circulating tumor markers for NETs
• Plasma 5-HIAA which is measured by high-performance liquid chromatography (HPLC)
• Levels of other tumor markers that are released by symptomatic and hormone-producing NETs in the blood will also be tested. These markers include hormones and peptides, such as somatostatin, pancreatic polypeptide, insulin, gastrin, glucagon, and vasoactive intestinal polypeptide (VIP)
• If the results of these tests suggest the presence of NETs, imaging tests will usually be carried out

Other blood tests for NETs may include:

• Full blood count (FBC)
• Kidney function tests (urea and electrolytes)
• Liver function tests
• Thyroid function tests
• Pituitary hormone screen, measuring hormones such as adrenocorticotropic hormone (ACTH), prolactin, growth hormone (GH), and cortisol
• Serum calcium and parathyroid hormone level tests, for all patients with pancreatic NETs, as a screening test for MEN-1 syndrome

5-HIAA is a 24-hour urine test that measures the amount of 5-hydroxyindoleacetic acid (5-HIAA) in the body. 5-HIAA is a substance that is broken down (metabolized) in the body from serotonin by an amino acid called tryptophan.

A high level of 5-HIAA in a 24-hour urine test sample is likely to confirm whether a person’s symptoms, such as flushing of the skin (particularly the face) and diarrhea, are due to carcinoid syndrome. However, this test may not detect other types of tumors, such as lung NETs as they do not produce 5-HIAA. In these cases, imaging techniques may be used to identify NETs suspected of being in the lungs.

Catecholamines is a collective term for the hormones adrenaline, noradrenaline, and dopamine. High levels of catecholamines or their metabolites in the urine or blood may indicate the presence of NETs. Catecholamines or their metabolites are usually measured in 24-hour urine samples.