Establishment of reference intervals for plasma metanephrines in seated position measured by LC-MS/MS and assessment of diagnostic performance in pheochromocytoma/paraganglioma.

Using the corresponding seated reference intervals for seated plasma MNs can reduce the unnecessary re-examinations of suspected patients with slightly elevated MNs. The cut-off value established by seated plasma MNs has good diagnostic performance in PPGL. Use of seated sampling is an acceptable practice and is more convenient and economical than supine sampling.