[Determination of serum metanephrines in the diagnosis of pheochromocytoma].

Presently, the diagnosis of pheochromocytoma rests upon the determination of urinary catecholamines, and specially metanephrines which offer 100% sensitivity and 97% specificity. The 24 hours urine collection is problematic for practical reasons and patient compliance. Serum metanephrines determination by HPLC (High Performance Liquid Chromatography) avoids these difficulties making the investigation easier. We report the results of serum metanephrine (MN) and normetanephrine (NMN) in 10 patients presenting with a pheochromocytoma histologically confirmed and without renal insufficiency, compared to 18 control healthy subjects, 33 patients suffering from hypertension and 11 patients with terminal renal failure on haemodialysis. The mean value of total metanephrines (MN + NMN) for the patients presenting with a pheochromocytoma is 326 +/- 206 nmol/l (range 76 to 718). In the control group without hypertension this value is 6.8 +/- 2.9 nmol/l (range 0.5 to 10.7) and for the control group with hypertension 25 +/- 27 nmol/l (range 7 to 138). For the patients with renal failure, the mean value is 471 +/- 201 nmol/l (range 188 to 920). Thus total metanephrines serum level values were found higher in the patients with a pheochromocytoma than in those with or without hypertension, but they were not discriminatory when the cases of renal insufficiency were included. CONCLUSION In case of a normal renal function, serum metanephrines determination for the diagnosis of pheochromocytoma gives, above a threshold value of 50 nmol/l, a sensitivity of 100% and a specificity of 94%.