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Chromogranin A

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Also known as: CgA
Formal name: Chromogranin A

The Test Sample

What is being tested?

This test measures the amount of Chromogranin A (CgA) in the blood. CgA is a protein found in and released from neuroendocrine cells. These are cells that are found in organs throughout the body and that have both nerve and endocrine aspects. Neuroendocrine cells, and the endocrine system glands that they are found in, can give rise to a variety of tumors, both benign and malignant. They include carcinoid tumors, pheochromocytomas, insulinomas, small cell lung cancers, neuroblastomas, and other neuroendocrine tumors. Many of these tumors release large quantities of hormones, such as serotonin, catecholamines, or insulin, continuously or intermittently, causing symptoms characteristic for that tumor. However, some neuroendocrine tumors do not release the expected hormones. In either case, neuroendocrine tumors are frequently associated with increased concentrations of CgA.

According to the American Cancer Society, there are about 11,000 to 12,000 neuroendocrine tumors or cancers diagnosed each year in the United States. Many more of these tumors may exist, but most remain small and do not cause any symptoms. When carcinoid tumors are discovered in asymptomatic patients during surgical procedures performed for other reasons, they are called "incidental" tumors. A small percentage of these tumors may eventually grow large enough to cause obstructions in the intestines or bronchial tubes of the lungs.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation may be needed or fasting may be required. Follow any instructions from the doctor or laboratory.