Chromogranin A (CgA)
Chromogranin A (CgA) is a protein made by certain hormone-producing (neuroendocrine) cells throughout the body, and the test measures its level in your blood. It is used mainly to help monitor specific known neuroendocrine conditions.
CgA is not a general screening or diagnostic test; it is most useful for following trends over time in people with an established neuroendocrine diagnosis. A single value has limited meaning on its own. Its interpretation depends closely on your medications and overall clinical situation.
An elevated CgA is not a diagnosis and is frequently influenced by common, benign factors. Proton pump inhibitors and other acid-reducing medications are a well-known cause of raised CgA, and reduced kidney function, chronic inflammation of the stomach lining, and certain other conditions can also lift it. Because of these effects, your clinician interprets CgA cautiously, often reviewing your medication list and repeating the test.
A low or normal CgA is generally unremarkable and is the common finding in most people not affected by the conditions or medications that raise it. It simply reflects a low level of this protein at the time of testing.
There is no universal target, and results are strongly affected by medications like acid reducers and by kidney function, so they should not be self-interpreted. A clinician should review CgA in the context of your medications, prior results, and why it was ordered.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.