Identification of potential interferents of methylmalonic acid: A previously unrecognized pitfall in clinical diagnostics and newborn screening.

Abstract

OBJECTIVES:

Determination of methylmalonic acid (MMA) from dried blood spots (DBS) is commonly performed in clinical diagnostics and newborn screening for propionic acidemia (PA) and methylmalonic acidemia. Isobaric compounds of MMA having the same mass can affect diagnostic reliability and quantitative results, which represents a previously unrecognized pitfall in clinical assays for MMA. We set out to identify interfering substances of MMA in DBS, serum and urine samples from confirmed patients with PA and methylmalonic acidemia.

METHODS:

Techniques included quadrupole time-of-flight high-resolution mass spectrometry (QTOF HR-MS), nuclear magnetic resonance (NMR) spectroscopy, liquid chromatography (LC) and tandem mass spectrometry (MS/MS).

RESULTS:

The five isobaric metabolites detected in DBS, serum and urine from PA and methylmalonic acidemia patients were confirmed as 2-methyl-3-hydroxybutyrate, 3-hydroxyisovalerate, 2-hydroxyisovalerate, 3-hydroxyvalerate and succinate using a series of experiments. An additional unknown substance with low abundance remained unidentified.

CONCLUSIONS:

The presented results facilitate the diagnostic and quantitative reliability of the MMA determination in clinical assays. Isobaric species should be investigated in assays for MMA to eliminate possible interference in a wide range of conditions including PA, methylmalonic acidemia, a vitamin B12 deficiency, ketosis and lactic acidosis.

• Authors: Péter Monostori, Markus Godejohann, Joachim Janda, Zsolt Galla, Gábor Rácz, Glynis Klinke, Ildikó Szatmári, Petra Zsidegh, Dirk Kohlmüller, Stefan Kölker, Georg F Hoffmann, Gwendolyn Gramer, Jürgen G Okun
• Journal: Clinical biochemistry (Clin Biochem) Vol. 111 Pg. 72-80 (Jan 2023) ISSN: 1873-2933 [Electronic] United States
• PMID: 36202155 (Publication Type: Journal Article)
• Copyright: Copyright © 2022 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.

Chemical References

• Methylmalonic Acid

Topics

• Infant, Newborn
• Humans
• Neonatal Screening (methods)
• Propionic Acidemia (diagnosis)
• Tandem Mass Spectrometry
• Methylmalonic Acid (urine)
• Reproducibility of Results
• Amino Acid Metabolism, Inborn Errors (diagnosis)