Chromogranin A (Chromogranin A, CgA)

Indications for the test

Chromogranin A (CgA) is recommended as part of the initial diagnostic work-up when a patient has symptoms that may be associated with neuroendocrine tumours:

• “hot flushes” — sudden heat spreading through the body and causing redness of the face and décolleté;
• rapid heartbeat;
• pain in the left half of the chest;
• spastic abdominal pain;
• nausea and vomiting;
• “causeless” loose stools;
• feeling of shortness of breath and difficulty exhaling.

These symptoms are part of the so-called carcinoid syndrome.

The chromogranin A tumour marker is also measured to monitor the clinical situation. A decrease in the level of this glycoprotein indicates a good response of the neuroendocrine tumour to therapy. And repeated testing after oncological treatment makes it possible to suspect a possible relapse in time.

During follow-up it is extremely important to have the tests done strictly in the same laboratory. The key reason is the lack of unified standardised test systems for these measurements. In other words, the sensitivity and evaluation methods of reagents differ from centre to centre, so a result obtained in one clinic may be incomparable with figures from another, which inevitably distorts the picture of real changes in the body.

Description of the test

Neuroendocrine neoplasms arise from specialised cells of the APUD system, diffusely scattered throughout the human body. The highest concentration of these structures is found in the bronchopulmonary tract and the gastrointestinal organs. Nevertheless, such cells are also present in the thymus, the pancreatic parenchyma, the gonads (ovaries), the prostate gland and the glandular tissue of the mammary glands, which explains the wide localisation of possible tumours.

Both normal and pathological APUD cells are able to secrete true hormones and hormone-like substances. They are biologically active and act on different tissues, leading to specific symptoms associated with changes in vascular tone and the lumen of the bronchial tree, intestinal motility, etc.

Chromogranin A is a protein secreted by cells of the diffuse neuroendocrine system. It is involved in the formation of hormones and hormone-like compounds. Importantly, regardless of whether the tumour has endocrine activity, the level of chromogranin A usually rises.