Abstract:

Objective To establish a method for spot urine free normetanephrine（NMN） and metanephrine（MN） by high performance liquid chromatography-electrochemical detection（HPLC-ED）,and to investigate the clinical application role. Methods Sample processing and chromatographic conditions were improved,and HPLC-ED for spot urine free NMN and MN was established. HPLC-ED was used to determine NMN and MN in 35 patients with pheochromocytoma,70 patients with primary hypertension,78 patients with adrenal mass but without pheochromocytoma and 44 healthy subjects. Creatinine（Cr）was determined as well. NMN/Cr ratio and MN/Cr ratio were calculated. Receiver operating characteristic（ROC） curve was used to evaluate the efficiency for diagnosing pheochromocytoma. Results The linear range of HPLC-ED for the determinations of NMN and MN was 25-2 500 μg/L. The determination limits [signal-to-noise ratio（R_SN）=3] were 5.9 and 11.3 μg/L,respectively. The average recovery was 92.8%-103.4%. The within-run coefficients of variation（CV） of high-concentration and low-concentration NMN were 3.7% and 2.2%,and the between-run CV of high-concentration and low-concentration NMN were 5.6% and 3.3%,respectively. The within-run CV of high-concentration and low-concentration MN were 4.3% and 2.7%,and the between-run CV of high-concentration and low-concentration MN were 5.1% and 3.4%,respectively. The concentrations of NMN and MN,NMN/Cr ratio and MN/Cr ratio in pheochromocytoma group were higher than those in hypertension group,adrenal space-occupying group and healthy control group（P<0.001）,and there was no statistical significance among hypertension group,adrenal space-occupying group and healthy control group（P>0.05）. ROC curve analysis showed that the area under curve（AUC） in diagnosing pheochromocytoma of urine free NMN,urine free MN,NMN/Cr ratio,MN/Cr ratio,plasma free NMN and plasma free NMN were 0.91,0.88,0.96,0.94,0.93 and 0.88,respectively. MN/Cr ratio in urine decreased to normal in 1 week after operation in pheochromocytoma patients,but the concentration of plasma MN in 2 patients was higher than that before operation,and in 1 patient,the plasma NMN concentration was higher than that before operation. Conclusions HPLC-ED has been successfully established to determine the concentrations of urine free NMN and MN. Compared with plasma free NMN and MN,spot urine free NMN and MN show good efficiency for the diagnosis of pheochromocytoma,which perform well to evaluate the prognosis of pheochromocytoma.

Key words: Normetanephrine, Metanephrine, High performance liquid chromatography-electrochemical detection, Pheochromocytoma