Harmonization of LC-MS/MS Measurements of Plasma Free Normetanephrine, Metanephrine, and 3-Methoxytyramine

Abstract

Background Plasma-free normetanephrine and metanephrine (metanephrines) are the recommended biomarkers for testing of pheochromocytoma and paraganglioma (PPGL). This study evaluated the status of harmonization of liquid chromatography-tandem mass spectrometry-based measurements of plasma metanephrines and methoxytyramine and clinical interpretation of test results. Methods 125 plasma samples from patients tested for PPGLs were analyzed in 12 laboratories. Analytical performance was also assessed from results of a proficiency-testing program. Agreement of test results from different laboratories was assessed by Passing-Bablok regression and Bland-Altman analysis. Agreement in clinical test interpretation based on laboratory specific reference intervals was also examined. Results Comparisons of analytical test results by regression analysis revealed strong correlations for normetanephrine and metanephrine (R ≥ 0.95) with mean slopes of 1.013 (range 0.975–1.078), and 1.019 (range 0.963–1.081), and intercepts of −0.584 (−53.736 to 54.790) and −3.194 (−17.152 to 5.933), respectively. The mean bias between methods was 1.2% (−11.6% to 16.0%) for metanephrine and 0.1% (−18.0% to 9.5%) for normetanephrine. Measurements of 3-methoxytyramine revealed suboptimal agreement between laboratories with biases ranging from −32.2% to 64.0%. Interrater agreement in test interpretation was >94% for metanephrine and >84% for normetanephrine; improvements in interrater agreement were observed with use of harmonized reference intervals, including age-specific cut-offs for normetanephrine. Conclusions Analytical methods for metanephrines are well harmonized between laboratories. However, the 16% disagreement in test interpretation for normetanephrine suggests use of suboptimal method-dependent reference intervals for clinical decision-making for this metabolite. Improved analytical methods and reference interval harmonization are particularly required for 3-methoxytyramine.

Commutability Assessment of Processed Human Plasma Samples for Normetanephrine and Metanephrine Measurements Based on the Candidate Reference Measurement Procedure

“…The normetanephrine and metanephrine concentrations in the 53 clinical plasma samples measured by the four routine assays and cRMP were compared using PB and BA analyses. Similar to previous findings [ 18 ], we observed good correlations between the cRMP and routine assays. Notably, we previously demonstrated that using patient-derived plasma samples assigned by the cRMP to recalibrate routine assays greatly decreased the large biases of the routine assays [ 11 ].…”

Reference intervals for plasma, urinary, and salivary concentrations of free metanephrines in dogs: Relevance to the diagnosis of pheochromocytoma

“…Plasma NMN concentrations in PCC dogs were markedly lower in our study than in previous studies, 13,14 whereas pMN concentrations were moderately lower to comparable. Similar to our study, LC‐MS/MS was used for free metanephrine measurement in both previous studies, which demonstrates good agreement among different laboratories 25 . The difference in metanephrine concentrations might be explained by the fact that, today, PCCs are diagnosed earlier in the course of the disease because of increasing awareness of this disease among clinicians and increasing use of diagnostic imaging.…”

“…A limitation of our study is that plasma free metanephrines of dogs with PCC, HC and NAI were measured by a different laboratory than the laboratory that was used for the reference population. However, both laboratories used LC‐MS/MS for metanephrine measurements, which has been shown to provide comparable results among laboratories 25 …”

Head/neck paragangliomas: focus on tumor location, mutational status and plasma methoxytyramine

“…Based on measurements of plasma MTY, at least a third of HNPGLs in our cohort were identified as biochemically active, which is similar to previous findings ( van Duinen et al 2013 , Smith et al 2021 ). However, most current methods of analysis do not reliably measure MTY at the concentration range necessary to establish the production of the metabolite by small tumors typical of HNPGLs ( Peitzsch et al 2021 ). An exception might be the recently described LC-MS/MS method described by van Faassen et al by which the use of in situ derivatization enables highly sensitive measurements of plasma MTY and other metabolites in as little as 50 µL of plasma ( van Faassen et al 2020 ).…”