Evaluation of diagnostic power of CgA determinations in neuroendocrine tumours (net_s)

Chromogranin A (CgA) is a 48 kDa hydrophilic acidic glycoprotein member of the granin family produced and stored together with biogenic amines and other peptide hormones in the secretory granules of the neuroendocrine cells, which are widespread in the whole organism and form the diffused endocrine system (DES). CgA is found in adrenal medulla, pancreatic islet cells, endocrine cells of the gastrointestinal tract and in sympathetic nervous system. CgA is physiologically released by exocytosis and may be detected in blood. Elevated circulating CgA levels have been demonstrated in serum or plasma of patients with various neuroendocrine tumors (NETs). Recent studies confirm that CgA is a useful marker for the diagnosis and follow-up of NETs. The aim of this study was to evaluate the diagnostic power of CgA determinations for the diagnosis of NETs. Analysis of the results of plasma CgA concentrations was performed in 41 patients with NETs. The control group was composed of healthy subjects (n=15). CgA plasma determinations were measured with the use of ELISA immunoenzymatic assay of commercially available kit Chromogranin A (DakoCytomation, Denmark). In order to investigate the diagnostic value of plasma CgA we plotted ROC (Receiver Operating Characteristic) curve and the area under the curve (AUC) was calculated. In our study, CgA plasma levels were statistically significantly higher (p<0.001) in patients with NETs compared to the control group. We calculated diagnostic sensitivity and specificity of CgA in NETs and positive and negative predictive values using the standard equations for the cut-off 18 U/l proposed by the manufacturer obtaining values of 71%, 87%, 93%, 52%, respectively. In conclusion, the DacoCytomation ELISA test for the determination of chromogranin A in plasma with the accepted cut-off value of 18 U/l that was used in this study has a good diagnostic power in detecting neuroendocrine tumors.