Serum Chromogranin A measurements are a first-line test for diagnosing carcinoid tumours, in conjunction with, or as an alternative to urine 5-hydroxyindoleacetic acid (5-HIAA).
Because of its ubiquitous distribution within neuroendocrine tissues, chromogranin A is a useful diagnostic marker for neuroendocrine neoplasms, including carcinoids, phaeochromocytomas, neuroblastomas, medullary thyroid carcinomas (MTC), some pituitary tumours, functioning and nonfunctioning islet-cell tumours and other amine precursor uptake and decarboxylation (APUD) tumours. It can also serve as a sensitive means for detecting residual or recurrent disease in treated patients. Carcinoid tumours, in particular, almost always secrete chromogranin A along with a variety of specific modified amines, chiefly serotonin (5-HT) and peptides. Carcinoid tumours are subdivided into gut carcinoids, arising from respiratory tract, stomach, pancreas, or duodenum (approximately 15% of cases); midgut carcinoids, occurring within jejunum, ileum, or appendix (70% of cases); and hindgut carcinoids, which are found in the colon or rectum (15% of cases). Carcinoids display a spectrum of aggressiveness with no clear distinguishing line between benign and malignant. In advanced tumours, morbidity and mortality relate as much, or more, to the biogenic amines and peptide hormones secreted, as to local and distant spread. The symptoms of this carcinoid syndrome consist of flushing, diarrhoea, right-sided valvular heart lesions, and bronchoconstriction.
A number of tumours that are not derived from classical endocrine or neuroendocrine tissues, but contain cells with partial neuroendocrine differentiation such as small cell carcinoma of the lung or prostate carcinoma, may also display elevated chromogranin A levels. The role of chromogranin A measurement is not well defined in these tumours, with the possible exception of prognostic information in advanced prostate cancer
0 – 3 nmol/L
To improve specificity patients should undergo an overnight fast before blood is sampled. PPI use can be a cause of a false positive result and this should be stopped, if possible, for 2 weeks prior to testing (Korse et al. 2011). H2 receptor antagonists do not interfere with the test.
Plasma – EDTA, sample to be centrifuged and the plasma stored and dispatched frozen.
Once the sample is taken it must be placed on ice or a cool pack and transported to the laboratory immediately.