Validation of the measurement of plasma metanephrines by liquid chromatography-Tandem mass spectrometry (LC-MS/MS)

The prevalence of arterial hypertension is very high all over the world. ~0.1% of subjects with secondary hypertension has a pheochromocytoma, a tumor producing catecholamines. The quantification of free plasma o-methylated metabolites, metanephrine (p-MN) and normetanephrine (p-NMN), is considered the most accurate test for both the diagnosis and monitoring of pheochromocytoma. The aim of this work was to validate of an assay for measuring plasma metanephrines by LC-MS/MS. Calibration curves showed good linearity (R2 >0.99). Intra-Assay repeatibility, assessed on two pools, normal and pathological, resulted in a CV of 5.1% and 3.9% for p-MN and 8.2% and 10.5% for p-NMN, respectively. Inter-Assay CVs were 15.9% and 11.9% for p-MN and 16.6% and 16.1% for p-NMN, respectively. The limit of detection was 8 pM for p-MN and 66 pM for p-MNM, while the limit of quantification was 26 pM for p-MN and 83 pM for p-NMN. 638 plasma samples were analyzed, providing a representative sample to assess potential clinical impact of the validated method.