Chromogranin A immunoradiometric assay in diagnosis of pheochromocytoma: comparison with plasma metanephrines and 123I-MIBG scan.

Objective: The aim of this study is to investigate the diagnostic performance of serum chromogranin A (CgA) and plasma metanephrines (MN) assays in the diagnosis of pheochromocytoma.

Methods: We enrolled 44 patients affected by histologically proved adrenal pheochromocytoma. All patients underwent abdominal computed tomography and whole body 123I-MIBG scan to stage the disease. One hundred healthy blood donors and 148 patients affected by essential hypertension were enrolled as controls. Serum CgA and plasma MN were assayed by immunoradiometric assay (IRMA) and high-performance liquid chromatography. Cut-off levels were selected to obtain 99% specificity in healthy control subjects.

Results: Both MN and CgA showed 95% sensitivity with comparable high specificity and diagnostic accuracy (96% and 96% for CgA, 94% and 95% for MN, respectively). By employing both markers and considering CgA or MN positivity, a 100% sensitivity was obtained with 95% accuracy. MN and CgA concentration clearly increased from controls to patients with pheochromocytomas (P<0.0001). A relationship between serum CgA (but not MN) and tumor mass was found (P<0.0001).

Conclusions: Both markers are sensitive and specific in chromaffin-tumors detection: CgA IRMA assay employed a simple and feasible technology and showed to be as sensitive and slightly more accurate than MN.