At a Glance
Why Get Tested?
To help diagnose and monitor carcinoid tumours and other neuroendocrine tumours
When to Get Tested?
When you have symptoms suggestive of a carcinoid tumour such as flushing, diarrhoea, and/or wheezing. When your doctor thinks you may have a carcinoid or other neuroendocrine tumour
Sample Required?
A blood sample taken from a vein in your arm
Test Preparation Needed?
You may be required to fast overnight prior to the specimen being taken and to temporarily discontinue certain medication beforehand. Please check the local laboratory instructions with your doctor prior to blood being taken.
The Test Sample
What is being tested?
This test measures the amount of Chromogranin A (CgA) in the blood. CgA is a protein found in and released from neuroendocrine cells. Neuroendocrine cells, and the endocrine system glands that they are found in, can give rise to a variety of tumours, both benign and malignant. They include carcinoid tumours, phaeochromocytomas, insulinomas, small cell lung cancers, neuroblastomas, and other neuroendocrine tumours. Many of these tumours release large quantities of hormones - such as serotonin, catecholamines, or insulin – continuously or intermittently, causing symptoms characteristic for that tumour. However, some neuroendocrine tumours do not release the expected hormones. In either case, neuroendocrine tumours are frequently associated with increased concentrations of CgA.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
You may be required to fast overnight prior to the specimen being taken and to temporarily discontinue certain medication beforehand. Please check the local laboratory instructions with your doctor prior to blood being taken.
The Test
How is it used?
The Chromogranin A test is used as a tumour marker. It may be requested in combination with or in place of 5-HIAA to help diagnose carcinoid tumours. It is also used to help monitor the effectiveness of treatment and detect recurrence of this tumour. Sometimes it may be requested with specific hormones, such as catecholamines, to help diagnose and monitor a phaeochromocytoma. It may also be used to detect the presence of other neuroendocrine tumours, even those that do not secrete hormones.
When is it requested?
CgA is requested along with other tests when a doctor suspects that a patient has a carcinoid tumour, phaeochromocytoma, or other neuroendocrine tumour. It may be requested periodically to help evaluate treatment effectiveness and monitor for tumour recurrence.
What does the test result mean?
Chromogranin A concentrations are normally low. Increased concentrations in a symptomatic patient may indicate the presence of a tumour 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 tumour burden – the mass of the tumour.
If concentrations of CgA are elevated prior to treatment and then fall, then treatment is likely to have been effective. If following treatment of the tumour concentrations begin to rise again, then the patient may have a recurrence of the tumour.
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 concentrations should be considered when interpreting test results.
A variety of methods are available for measuring CgA. 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.
Common Questions
Ask a Laboratory Scientist
Article Sources
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
