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Functional vitamin B12 deficiency: Improving methylmalonic acid reference intervals in urine
Jose A Delgado1, María I Pastor García1, Nuria Márquez Jiménez1
1Department of Laboratory Medicine, Hospital Universitari Son Espases, Palma, Spain.
Summary
This study establishes reference intervals for urinary methylmalonic acid (MMA), a key biomarker for vitamin B12 deficiency. Results show a link between elevated MMA and low vitamin B12 levels, aiding in deficiency diagnosis.
Area of Science:
- Clinical Chemistry
- Nutritional Biochemistry
- Diagnostic Biomarkers
Background:
- Vitamin B12 deficiency is a common concern in laboratory diagnostics.
- Methylmalonic acid (MMA) is recognized as a sensitive biomarker for detecting vitamin B12 deficiency.
- Establishing reliable reference intervals for MMA is essential for accurate diagnosis.
Purpose of the Study:
- To determine the biological reference interval for urinary MMA.
- To investigate the influence of age, sex, and vitamin B12 status on urinary MMA concentrations.
- To assess the utility of MMA in identifying functional vitamin B12 deficiency.
Main Methods:
- Prospective observational study design.
- Exclusion of individuals with confounding factors (supplementation, specific pathologies, pregnancy, antibody interference).
- Non-parametric calculation (1st-99th percentiles) for reference interval determination based on age and sex groups.
Main Results:
- A single reference interval for urinary MMA was established: [0.52-5.75] mmolMMA/mol creatinine.
- 100% of individuals with MMA above the upper limit of the reference interval had a total vitamin B12 concentration ≤ 238 pmol/L.
- This suggests a strong correlation between elevated urinary MMA and low vitamin B12 levels.
Conclusions:
- Establishing optimal reference intervals for urinary MMA is critical for diagnosing functional vitamin B12 deficiency.
- The study highlights the importance of MMA as a biomarker in this context.
- Defining a precise cut-off for total vitamin B12 to indicate subclinical deficiency based on MMA requires further investigation.
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