Also known as: CgA
Name: Chromogranin A
Related tests: Plasma and urine catecholamines, Tumour markers, 5-hydroxyindoleacetic acid, Serotonin
Why have this test?
It can help diagnose and monitor carcinoid tumours and other tumours of neuroendocrine origin.
When to have this test?
When a carcinoid tumour or other neuroendocrine tumours are suspected.
What samples are required?
A blood sample taken from a vein.
What is being measured?
This test measures the concentration of chromogranin A (CgA) in the blood. CgA is a protein found in neuroendocrine cells and released by them into the blood. Neuroendocrine cells, and the endocrine glands that contain them, can give rise to a variety of benign and malignant tumours. These include carcinoid tumours, phaeochromocytoma, insulinoma, small cell lung cancer, neuroblastoma and others. Many of these tumours produce hormones such as serotonin, catecholamines or insulin; these hormones may be produced continuously or intermittently, causing symptoms typical of these tumours. However, not all neuroendocrine tumours produce these substances. In either case, neuroendocrine tumours are often associated with a raised blood concentration of CgA.
How is the sample collected for testing?
The blood sample is taken from a vein.
Is any preparation needed to ensure the quality of the sample?
No preparation is needed
How is it used?
When is it requested?
What does the test result mean?
Is there anything else I should know?
How is it used?
Chromogranin A is used as a tumour marker. This test may be requested together with or instead of 5-HIAA to help diagnose carcinoid tumours. It is also used to monitor the effectiveness of treatment of a tumour already diagnosed and to detect recurrence. In some cases it may be requested together with other hormones, such as catecholamines, to help diagnose and monitor phaeochromocytoma. It can also be used when other types of endocrine tumour are suspected, including those that do not secrete hormones.
When is it requested?
Chromogranin A, alone or together with other tests, is requested when the doctor suspects that a patient has a carcinoid tumour, a phaeochromocytoma or another type of neuroendocrine tumour. The test may be requested periodically to assess the effectiveness of treatment and to detect recurrence.
What does the test result mean?
The concentration of chromogranin A in the blood is normally low. Raised concentrations in a patient with symptoms may indicate a tumour, but give no information about its type or location. The concentration is not related to the severity of symptoms but is proportional to the size of the tumour mass.
If the chromogranin A concentration is high before treatment starts and falls after treatment, the treatment has probably been effective. If the concentration starts to rise during monitoring, the tumour has probably come back.
Is there anything else I should know?
CgA can be raised in other situations, such as liver disease, inflammatory bowel disease, kidney failure and stress. All these conditions must be taken into account when interpreting the result.
No analytical method for measuring CgA has yet been approved by the Food & Drug Administration (the US government agency that regulates the marketing of products including medicines and in vitro diagnostic devices). The various commercially available methods differ and give results that cannot be compared with one another, so a patient being monitored should always use the same laboratory.
1. Should everyone have the chromogranin A test?
2. How can a carcinoid or neuroendocrine tumour be located?
3. How can a benign form be distinguished from a malignant one?
1. Should everyone have the chromogranin A test?
No. This test may only be requested to help diagnose and monitor carcinoid tumours and other tumours of neuroendocrine origin, which are uncommon. Most people will never need this test.
2. How can a carcinoid or neuroendocrine tumour be located?
With imaging techniques such as X-rays, computed tomography (CT) or magnetic resonance imaging (MRI). In some cases surgery is needed.
3. How can a benign form be distinguished from a malignant one?
With a biopsy, or by surgically removing the tumour, followed by examination by a pathologist.