Chromogranin A
Also known as: CgA
Formal name: Chromogranin A
The Test
How is it used?
The Chromogranin A test is used as a tumor marker. It may be ordered in combination with or in place of 5-HIAA to help diagnose carcinoid tumors. It is also used to help monitor the effectiveness of treatment and detect recurrence of this tumor. Sometimes it may be ordered with specific hormones, such as catecholamines, to help diagnose and monitor a pheochromocytoma. It may also be used to detect the presence of other neuroendocrine tumors, even those that do not secrete hormones.
When is it ordered?
CgA is ordered along with other tests when a doctor suspects that a patient has a carcinoid tumor, pheochromocytoma, or other neuroendocrine tumor. It may be ordered periodically to help evaluate treatment effectiveness and monitor for tumor recurrence.
What does the test result mean?
Chromogranin A concentrations are normally low. Increased levels in a symptomatic patient may indicate the presence of a tumor but will not tell the doctor what type it is or where it is. The quantity of CgA is not associated with the severity of a patient's symptoms but is associated with the tumor burden - the mass of the tumor.
If concentrations of CgA are elevated prior to treatment and then fall, then treatment is likely to have been effective. If monitored levels begin to rise, then the patient may have a recurrence of the tumor.
Is there anything else I should know?
CgA concentrations may be elevated in other conditions, such as liver disease, inflammatory bowel disease, renal insufficiency, and with stress. These possible causes for elevated CgA levels should be considered when interpreting test results.
There are currently not any FDA approved Chromogranin A tests. Those CgA tests that have been developed and validated by laboratories will all be slightly different, and their results will not be interchangeable. For this reason, if a patient is having more than one CgA test performed (such as for monitoring), then his or her doctor will generally send each sample to the same laboratory.
