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Published on: June 24, 2019
Comparison of two methods for measuring methylmalonic acid as a marker for vitamin B12 deficiency
Rima Obeid1, Jürgen Geisel2, Wolfgang Herrmann2
11Department of Clinical Chemistry and Laboratory Medicine, University Hospital of the Saarland, Homburg/Saar, Germany2Aarhus Institute of Advanced Studies, University of Aarhus, 8000 Aarhus C, Denmark.
Background:
Methylmalonic acid (MMA) is a functional marker of vitamin B12 status and a valuable diagnostic tool. The gas chromatography mass spectrometry (GCMS) MMA assay has been used for decades in clinical studies.
Methods:
In this study, we compared a newly developed liquid chromatography tandem mass spectrometry assay for MMA (ClinMass® Complete Kit) with the GCMS method and further measured other relevant vitamin B12 markers (homocysteine, total B12 and holotranscobalamin) to validate the new liquid chromatography combined with tandem mass spectrometry (LC-MS/MS) method. For this purpose, 138 samples that were sent to our routine laboratory total B12 assay were used.
Results:
The GCMS and LC-MS/MS assays showed a strong correlation (r=0.92, p<0.001) particularly at low holoTC levels (deficiency is more probable). Forty six cases had MMA>300 nmol/L with both methods. Only five subjects showed MMA GCMS>300 nmol/L, but MMA LC-MS/MS≤300 nmol/L. However, the LC-MS/MS method showed a slightly better correlation with other B12 markers (holoTC, total B12). In addition, the LC-MS/MS method offers several advantages over the GCMS method, such as saving time and costs, precision, flexibility and popularity in modern labs.
Conclusions:
The new LC-MS/MS assay for MMA showed an excellent correlation to the GCMS method. The two methods showed similar agreements with other vitamin B12 markers.
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