- Also Known As:
- Serum CgA
- CgA Blood Test
- Chromogranin A Blood Test
Test Quick Guide
Chromogranin A (CgA) is a protein released by neuroendocrine cells. Neuroendocrine cells are found in many organs in the body and have characteristics of both nerve cells and cells that make hormones.
A test for chromogranin A measures the amount of CgA in the blood. This is known as a tumor marker test because CgA can be released in higher than normal levels in patients with tumors of the neuroendocrine system.
There is no consensus among experts about the optimal use of CgA testing for people with neuroendocrine tumors (NETs). Chromogranin A may be measured to help evaluate the effectiveness of treatment for NETs. CgA levels may also be considered when assessing prognosis, and, less often, they may be a part of the diagnostic process for NETs.
About the Test
Purpose of the test
The purpose of CgA testing is to measure the amount of CgA in the blood. CgA levels can be elevated in patients with a range of health conditions. However, CgA testing is typically reserved for the diagnosis and management of patients with neuroendocrine tumors.
Neuroendocrine tumors (NETs) develop in the cells of the neuroendocrine system and can be cancerous or non-cancerous. NETs can begin in many organs but are most common in:
- The gastrointestinal tract, including the large intestine, small intestine, and the appendix
- The lungs
- The pancreas
There are different ways that CgA testing may be used for tests related to NETs. Your doctor may order a CgA test for one of several reasons:
- Monitoring treatment response: For people with some neuroendocrine tumors, CgA levels may provide information about whether treatment is working. CgA may also be measured over time to check for changes in levels that could indicate a possible recurrence of the tumor after treatment is completed.
- Estimating prognosis: Testing CgA levels may help doctors understand prognosis, or the chance of recovery, in patients with neuroendocrine tumors.
- Diagnosing a neuroendocrine tumor: Less often, a CgA test may be used for diagnosis in a person who has symptoms of a neuroendocrine tumor. There are limitations to using CgA testing in diagnosis because CgA levels can be elevated by other health conditions.
What does the test measure?
CgA testing measures the amount of the chromogranin A protein in a sample of blood. CgA levels are measured in nanograms per milliliter (ng/mL).
CgA is produced by cells of the neuroendocrine system. Neuroendocrine cells have properties of both nerve cells and hormone-producing cells. Neuroendocrine cells receive signals from the nervous system that trigger them to release hormones and other substances, including CgA, into the blood. There are neuroendocrine cells in organs throughout the body.
Neuroendocrine tumors develop when there is abnormal growth of neuroendocrine cells. Depending on the type of NET, the size of the tumor, and whether it has spread, CgA levels may become elevated. For this reason, CgA testing can play a role in the care of patients with neuroendocrine tumors.
When should I get a chromogranin A test?
The most common situation for using chromogranin A testing is if you have already been diagnosed with a neuroendocrine tumor and your doctor wants to see how the tumor is responding to treatment. In some situations, your doctor may evaluate your CgA level to see if the cancer has come back.
Less frequently, CgA testing may be ordered to help diagnose a NET. This type of testing may be recommended if:
- You have symptoms that could be caused by a neuroendocrine tumor
- You have no symptoms, but a possible NET is found during surgery or imaging tests for an unrelated health issue
If you are diagnosed with a neuroendocrine tumor, your doctor may recommend CgA testing to help assess your situation and the prognosis of your condition.
Finding a Chromogranin A Test
How to get tested
A test to measure the levels of CgA requires a blood draw that must be ordered by a doctor. The blood sample is typically taken in a doctor’s office, medical clinic, or laboratory and sent for analysis.
Can I take the test at home?
At-home testing for CgA is not commercially available. Testing must be ordered by a doctor and performed in a medical setting.
How much does the test cost?
The cost of testing CgA levels depends on a number of factors. Health insurance status, where the test is performed, and whether other tests are done at the same time can impact how much testing costs.
There are several laboratory methods used to determine CgA levels. The cost of your test will depend on the laboratory method used.
Questions about the cost of CgA testing can be directed to your health care provider, the facility where you are receiving care, or your health insurance provider. They may be able to offer information about out-of-pocket costs for testing such as co-pays and deductibles.
Taking a Chromogranin A Test
A blood sample is needed to measure CgA levels. The blood sample is typically collected in a medical office or laboratory.
Before the test
It is important to speak with your health care provider before CgA testing to learn if any special test preparation is required. Following your doctor’s instructions on how to prepare for CgA testing will help ensure an accurate test result.
You may be asked to fast before having your blood drawn. Fasting means not eating or drinking anything but water for 8 to 12 hours before your test.
Some medications can affect the results of your CgA test. For that reason, your doctor may ask you to stop taking certain medications before testing.
During the test
You will need to provide a sample of blood for your CgA test. Typically, the person drawing your blood will collect a sample from a vein in your arm.
Before your blood draw begins, an elastic band is placed around the upper part of your arm to increase the flow of blood. The area is then cleaned with an antiseptic wipe.
A needle is inserted into the vein to start the flow of blood. Your blood is collected in a small test tube or vial connected to the needle. When the required amount of blood is collected, the needle is removed from your vein.
The procedure to draw your blood lasts only a few minutes. You may feel a sting or slight pain when the needle is inserted, but any discomfort does not usually last long.
After the test
After the needle has been removed from your vein, pressure is applied to the area with gauze. This helps stop the flow of blood and prevent bruising. Finally, a bandage is placed over the area where the sample was taken.
Blood draws are a common medical procedure. Typically, you can return to your normal activities right away.
If you were asked to stop medications before having your blood drawn for your CgA test, speak with your doctor for instructions about when to start taking them again.
Chromogranin A Test Results
Receiving test results
The results of your CgA test should be available to your doctor within a few business days. Your health care provider may call you or schedule an appointment to discuss the result and what it means for your health.
If you have access to an online health portal, your results may also be available online. In some cases, the doctor may send a copy of your test results through the mail.
Interpreting test results
Your test report will have information about the level of CgA detected in your blood expressed in nanograms per milliliter (ng/mL). You will also see a reference range used to interpret your result. The reference range is what the laboratory considers to be the expected CgA level for a healthy person.
Your doctor will interpret your test result in relation to this reference range and in the context of your health situation.
Some doctors use CgA testing to evaluate the effectiveness of treatment for a NET. Elevated CgA levels may be a sign that the tumor is progressing or has recurred, but CgA testing alone cannot determine how well treatment has worked.
CgA levels may also be considered in assessing the prognosis of a NET. For some types of NETs, high CgA levels could suggest a less favorable prognosis. However, many other factors besides CgA affect prognosis, so CgA alone cannot determine the most likely course of the disease.
Your doctor is in the best position to help interpret the results of your CgA test along with the results of any other tests that were performed related to the diagnosis or monitoring of a neuroendocrine tumor.
Are test results accurate?
Although CgA is the most widely used tumor marker in patients with a suspected or confirmed neuroendocrine tumor, CgA testing has limitations.
CgA levels can be elevated in a range of health conditions other than neuroendocrine tumors. For example, CgA levels may increase in people with irritable bowel disease, chronic hepatitis, liver failure, inflammatory diseases, and renal failure. Several medications can also cause an elevation in CgA levels.
As a result, CgA testing for neuroendocrine tumors may produce an elevated result that shows signs of a NET when a person does not actually have this kind of tumor.
Multiple laboratory tests are available to measure the amount of chromogranin A in the blood. Results can vary depending on the test that is used. If CgA levels are being monitored over time, it is important that the same test method be used each time.
If you have questions about the reliability of your test results, you can speak with your doctor or the laboratory that performed the test. General information about the reliability of laboratory testing can be found in our resource: How Reliable is Laboratory Testing?.
Do I need follow-up tests?
CgA levels can’t be used alone for the diagnosis and management of neuroendocrine tumors. Your doctor will perform other tests to confirm a diagnosis or recurrence or to determine whether your treatment is working. Your doctor may order other laboratory tests, imaging tests, or a biopsy to learn more about your condition.
Questions for your doctor about test results
It is normal to have questions about your test result and what it means for your health. This list of questions can be helpful as you talk with your doctor about your results:
- What is the result of my CgA test, and is it within the reference range?
- Will you order other tests to understand my elevated CgA level?
- What does my CgA level mean for my prognosis?
- What does my CgA level tell you about how well treatment is working?
- Could other things besides a neuroendocrine tumor have affected my CgA level?
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