Diagnostic Use
CGA is useful for diagnosis and monitoring of patients with carcinoid tumor, pheochromocytoma, paraganglioma, neuroblastoma, medullary thyroid carcinoma, islet cell tumours, gastrointestinal APUD tumors, and some pituitary adenomas.
Some tumors that are not derived from neuroendocrine tissues, but contain cells with partial neuroendocrine differentiation, such as small-cell carcinoma of the lung or prostate carcinoma, may also display elevated CGA levels.
Interpretation
Carcinoid tumours are neuroendocrine tumours that usually arise from enterochromaffin cells, which are found scattered throughout the body but occur principally in the submucosa of the intestine and main bronchi. The carcinoid syndrome is caused by systemic release of one or more of the secretory products: amines, polypeptides, and or prostaglandins.The most common manifestations of carcinoid syndrome are vasomotor changes (flushing), gastrointestinal hypermotility (diarrhoea), bronchospasm (wheezing, dyspnoea) and hypotension.
An attack of carcinoid syndrome may be provoked by emotional stress, heat, ingestion of particular foods or alcohol, straining at stool, or exogenous stimulation with adrenaline, dopamine or gastrin.
Carcinoid crisis with severe flushing and diarrhoea leading to dehydration, hypotension, and arrhythmias, along with unconsciousness, is a potentially life threatening complication.
To confirm the diagnosis, 24 hour urinary 5-HIAA is recommended (with dietary restrictions). Blood CgA and serotonin levels are useful for monitoring the treatment of established disease and may also be use when 5-HIAA levels are equivocal. CgA levels may be used to establish tumour burden.
Chromogranin A is not specific for neuroendocrine tumours and is not suitable as a screening test for primary diagnosis of carcinoid tumours. Elevated levels may also be seen in renal impairment, liver failure, inflammatory bowel disease and prostatic carcinoma. Proton pump inhibitors may also markedly elevate levels.
Test Method
Principle: Immunoassay
Assay: BRAHMS
Analyser: BRAHMS Kryptor Compact Plus