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.

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.

Chromogranin A concentrations are normally low. Increased levels 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 monitored levels begin to rise, then the patient may have a recurrence of the tumour.

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.

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.