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. 2021 Aug 5;67(8):1098-1112.
doi: 10.1093/clinchem/hvab060.

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

Mirko Peitzsch  1 , Talia Novos  2 , Denise Kaden  1 , Max Kurlbaum  3 , Antonius E van Herwaarden  4 , Daniel Müller  5 , Jo Adaway  6 , Eric Grouzmann  7 , Brett McWhinney  8 , Kirsten Hoad  9 , Gerald Woollard  10 , Ido Kema  11 , Christopher Boot  12 , Martin Fassnacht  3 , Fred Sweep  4 , Tze P Loh  13 , Andrea R Horvath  2 , Graeme Eisenhofer  1   14
Affiliations

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

Mirko Peitzsch et al. Clin Chem. .

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.

Keywords: LC-MS/MS; harmonization; metanephrines; paraganglioma; pheochromocytoma; standardization.

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