Plasma or serum, which is the better choice for the measurement of metanephrines?

Abstract

Background

Measurement of metanephrines (MNs: metanephrine [MN] and normetanephrine [NMN]) is recommended for the initial biochemical diagnosis of pheochromocytoma and paraganglioma. Despite some drawbacks, plasma is commonly used for sampling. Here, we determined the feasibility of using serum, as an alternative to plasma, by comparing MNs in plasma and serum and evaluating the stability of MNs in serum. MNs obtained from serum, EDTA plasma, and heparin plasma were measured using LC-MS/MS immediately or after storage at 4 °C for 24 h, 72 h, and 7 days, and at −80 °C for 7 days, after sample collection. The differences between sample stability at given time points were compared using one-way ANOVA and Students’ paired t-test, and the mean percent deviation was compared with total change limit (TCL). No significant difference was observed in MN and NMN between serum and EDTA plasma, and the mean percent deviation of the results obtained from serum compared to that from EDTA plasma was within the TCL. However, the difference of MN between EDTA plasma and heparin plasma exceeded the TCL. Both MNs in EDTA plasma and heparin plasma showed a significant decreasing trend at 4 °C with time (p < .01), while those in serum were relatively stable, with the mean percent deviation not exceeding the TCL at any time point or temperature. In conclusion, MNs measurement did not significantly differ between EDTA plasma and serum when measured immediately after collection, and MNs in serum were more stable than that in plasma.

Keywords:

• Metanephrines
• liquid chromatography tandem mass spectrometry
• plasma
• serum
• stability

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the Ethics Committee of Peking Union Medical College & Chinese Academy of Medical Sciences, Peking Union Medical College Hospital and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards (ZS-2485).

Informed consent

Informed consent was obtained from all individual participants included in the study.

Disclosure statement

All authors declares that he/she has no conflict of interest.

Additional information

Funding

This study was funded by the National Natural Science Foundation of China [81702060], and Beijing Key Clinical Specialty for Laboratory Medicine - Excellent Project (No. ZK201000). The funding bodies were not involved in conducting or analyzing this work or in the decision to publish. The authors have no additional financial disclosures.