Chromogranin A (CgA): structure, biological function, pre-analytical, analytical, and clinical aspects of its measurement in blood

Summary Chromogranin A (CgA) is a main nonspecific neuroendocrine tumour (NET) marker. Currently few commercial assays are available: RIA, IRMA, ELISA, CLIA, TRACE. There are many factors: in vivo, in vitro and coexisting diseases which can influence the CgA blood concentration. Elevated CgA levels in blood can be usually detected in: gastroenteropancreatic neuroendocrine tumours (GEP-NET), pheochromocytoma, neuroblastoma, MEN syndromes, bronchopulmonary NETs, medullary thyroid carcinoma, small-cell lung carcinoma, and some other very rare NETs. CgA measurement became a routine investigation in the diagnosis of GEP-NET, but is especially helpful in monitoring the effects of their treatment. CgA can be considered as a complementary investigation in the diagnostic procedure of pheochromocytoma. In patients with multiple endocrine neoplasia (MEN) investigation of CgA level may be used in monitoring eventual coexistence or appearance with time of carcinoid, pancreatic neuroendocrine tumour or pheochromocytoma.