Comparison between two commercially available chromogranin A assays in detecting neuroendocrine differentiation in prostate cancer and benign prostate hyperplasia.

BACKGROUND: Chromogranin A (CgA) is the neuroendocrine (NE) marker most frequently employed in detecting NE differentiation in prostate cancer patients, either at the tissue level or in the general circulation. METHODS: We compared the two commercially CgA assay kits in detecting NE differentiation, in benign hyperplasia (BPH) or prostate cancer (PC) patients (pts). 170 pts with BPH, 107 with BPH+inflammation, and 136 PC pts entered the study. CgA was measured in each patient with the immunoradiometric assay (IRMA) and with the enzyme-linked immunoabsorbent assay (ELISA). RESULTS: A moderate relationship was found between CgA measured with IRMA and ELISA in the whole population (Spearman's R=0.65, p<0.05), in BPH pts (R=0.76, p<0.05), in BPH+inflammation pts (R=0.53, p<0.05) and in PC pts (R=0.60, p<0.05). Twenty-two out of 62 pts (35.4%) with elevated ELISA CgA did not have increased IRMA CgA; by contrast, 21/61 pts (34.4%) with elevated IRMA CgA were not recognized as abnormal by the ELISA kit. CONCLUSIONS: CgA measured by the two assays provided a significant discordance rate, suggesting that the two kits might elicit different information.