Adrenal pheochromocytomas are neoplasms characterized by catecholamine excess. We recently reported on the diagnostic value of plasma metanephrines measured by RIA for the diagnosis of pheochromocytoma. However, RIA may not be used in many laboratories.
This study evaluated plasma and urinary metanephrines determined by a newly available ELISA as well as serum chromogranin A (CgA) for the diagnosis of pheochromocytoma. Spontaneous blood samples and 24h-urine samples were collected in 154 subjects, including 24 histologically proven pheochromocytomas, 17 aldosterone-secreting and 21 cortisol-secreting adrenal adenomas, 30 nonfunctioning adrenal masses, 16 patients with essential hypertension and 42 healthy normotensive volunteers. Plasma and urinary metanephrine (MN) and normetanephrine (NMN) as well as CgA were determined and putative thresholds calculated by ROC analysis.
Plasma NMN showed highest sensitivity (89.5%) and specificity (98.3%) using a threshold of 167 pg/ml, with lower sensitivity (85.7%) and specificity (91.8%) for urinary NMN by a threshold of 318 μg/24 h. Plasma and urinary MN demonstrated a much lower sensitivity (68.4% resp. 71.4%) and specificity (90.0% resp. 77.6%) using a threshold of 26 pg/ml and 90 μg/24 h respectively. Analysis of the combination of plasma metanephrines revealed a sensitivity of 89.5% and a specificity of 90.0%. Considering both urinary parameters demonstrated a slightly higher sensitivity (92.9%) with lower specificity (77.6%). ROC analysis revealed a threshold of 215pg/l for CgA with rather low sensitivity (73.9%) and specificity (74.2%). A weak positive correlation was found between the tumor size of pheochromocytomas and plasma MN (r=0.53, P<=0.05) as well as CgA (r=0.60, P<=0.01).
In conclusion, plasma metanephrines measured by ELISA are convenient and reliable parameters for the diagnosis of pheochromocytoma. In contrast, CgA demonstrated poor sensitivity and specificity.