Chromogranin A

A Chromogranin A test measures the amount of chromogranin A (CgA), a protein released by neuroendocrine cells (cells of endocrine (hormonal) and nervous systems) in the blood. It is also known as a tumor marker test because higher than normal levels of CgA are usually present in people with neuroendocrine tumors (NETs).

Neuroendocrine cells are found in various organs in the body and resemble both nerve cells and cells that make hormones. NETs develop due to abnormal growth of the neuroendocrine cells and they may be cancerous or non-cancerous. Such tumors occur most commonly in the gastrointestinal tract (GIT) (including large intestine, small intestine, and appendix), lungs, and pancreas. The symptoms of NETs may vary depending on the affected organs. For example, a tumor in the lung may cause wheezing or a persistent cough while a tumor in the GIT may cause diarrhea, constipation, or persistent stomach pain. It should be noted that a person may or may not show any symptoms and still demonstrate high CgA levels or develop a NET.

CgA levels can be elevated in people with many health conditions like atrophic gastritis, and impaired liver or kidney function. However, a Chromogranin A test typically helps with establishing a diagnosis and monitoring individuals with NETs. This test is the first-line diagnostic test for detecting carcinoid tumors, a type of NET. CgA may also be measured to help determine treatment response in NETs. Doctors may order this test to understand the course of the disease in known cases of NETs. In a few instances, your doctor may advise the test to check if the cancer has recurred.

There are no special preparations required before getting a Chromogranin A test done. However, it is recommended that a person discontinues the use of proton pump inhibitors for at least 2 weeks prior to sample collection to maintain test accuracy. Discontinuation should be with prior consent from the treating physician.

Test result ranges are approximate and may differ slightly between different labs depending on the methodology and laboratory guidelines. Talk to your doctor about your specific test results. Narrate your complete medical history to help the doctor correlate your clinical and laboratory findings. The results will help them determine your medical condition and formulate your overall treatment plan.