To help diagnose and monitor carcinoid tumors and other neuroendocrine tumors and assess the response to these tumors' treatments
Chromogranin A
Chromogranin A
Also Known As
CgA
This article was last reviewed
on
This article waslast modified
on June 5, 2020.
At a Glance
Why Get Tested?
When To Get Tested?
When you have symptoms suggestive of a carcinoid tumor, such as flushing, abdominal pain or discomfort followed by diarrhea, and/or wheezing; when your healthcare provider thinks that you may have a carcinoid or other neuroendocrine tumor
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
Fasting may be required; stopping certain medications may be necessary. Follow any instructions from your healthcare provider or laboratory. However, do not stop taking your medication(s) unless instructed to do so by your healthcare practitioner.
Accordion Title
Common Questions
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How is the test used?
The chromogranin A (CgA) test is used as a tumor marker. It may be ordered alone or in combination with a 5-HIAA test to help diagnose carcinoid tumors. CgA may also be used to detect the presence of other tumors arising from neuroendocrine cells.
A CgA test may also be used to help monitor the effectiveness of treatment and detect recurrence of these tumors.
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When is it ordered?
A CgA test is ordered along with other tests when a healthcare practitioner suspects that your signs and symptoms are due to a carcinoid tumor or other neuroendocrine tumor.
Some signs and symptoms may include:
- Flushing of the face and neck (appearance of deep red color, usually with sudden onset)
- Diarrhea, nausea, vomiting, abdominal pain, and signs of intestinal blockage
- Rapid heart rate
- Chest pain, wheezing, coughing, difficulty breathing
This test may be ordered periodically to help evaluate treatment effectiveness and monitor for tumor recurrence.
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What does the test result mean?
The level of chromogranin A in the blood is normally low. If you have no signs or symptoms and a normal level of CgA, it is unlikely you have a neuroendocrine tumor. However, no test is one hundred percent accurate, and it is possible to have a neuroendocrine tumor, even if the level of CgA is normal.
An increased CgA level when you have symptoms may indicate the presence of a tumor, but it is not specific for the type of tumor or its location. In order to diagnose the condition, the tumor itself must be located, biopsied, and examined by a pathologist. Your healthcare practitioner will frequently follow an abnormal test result with an order for an imaging scan to help locate any tumor(s) that may be present.
Not all patients with a neuroendocrine tumor have typical signs and symptoms. Some tumors do not produce the hormone associated with that tissue or only produce it intermittently.
The level of CgA is proportional to the tumor burden (the mass of the tumor). If levels of CgA are elevated prior to treatment and then fall after treatment is started, then treatment is likely to have been effective. If following the treatment, the monitored levels begin to rise; then you may have a recurrence of the tumor.
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Besides a neuroendocrine tumor, what else can cause elevated CgA levels?
CgA levels may be elevated in conditions such as liver disease, inflammatory bowel disease, pancreatitis, chronic bronchitis, renal insufficiency, and stress. These possible causes for elevated CgA levels should be considered when interpreting test results.
Chromogranin A can also be increased in people who take proton pump inhibitors (PPIs) or histamine 2 receptor antagonists, which are drugs that reduce the amount of stomach acid. Other medications that could alter the CgA level are serotonin reuptake inhibitors, which are used for the treatment of depression. It is sometimes recommended to avoid these medications to obtain reliable CgA results. Follow the instructions from your healthcare provider or laboratory and do not stop taking your medications unless instructed by your healthcare practitioner.
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How does a healthcare practitioner locate the carcinoid or neuroendocrine tumor?
This is usually accomplished through the use of imaging scans such as x-rays, computed tomography (CT), or magnetic resonance imaging (MRI). In some cases, surgery is required to find the tumor. For more on these imaging tests, visit RadiologyInfo.org.
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How does the healthcare practitioner tell whether a tumor is benign or cancerous?
In order to determine whether the tumor is benign or cancerous, the healthcare practitioner will need to perform a biopsy or remove the tumor surgically. The tumor is sent to the laboratory, where a pathologist examines the tumor cells using a microscope and makes a diagnosis. (For more on this, read the article on Anatomic Pathology.)
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Is there anything else I should know?
There is currently no FDA-approved chromogranin A test, and FDA approval for this test is not required. Those CgA tests that have been developed and validated by individual laboratories are all slightly different, and their results are not interchangeable. When monitoring CgA levels over time, the tests should be performed by the same laboratory and the same method so that values can be compared.