L’acide méthylmalonique urinaire comme biomarqueur de la déficience en vitamine B12 : est-il associé à la sévérité des symptômes neurologiques?
Bibliographic record
Abstract
Vitamin B12 deficiency is widespread among the elderly, affecting 5-15% of the population and up to 42% of hospitalized patients. This often mild to moderate deficiency is mainly due to poor absorption or inadequate dietary intake. It can lead to neurological complications such as peripheral neuropathy, cognitive impairment and balance disorders. Early diagnosis and treatment are essential to prevent irreversible damage. Urinary methylmalonic acid (uMMA) has been proposed as a non-invasive and cost-effective biomarker of vitamin B12 status, but its clinical applicability remains underexplored. The aim of this study is to examine the association of the urinary uMMA/creatinine ratio with neurological symptoms and assess the response to supplementation in the elderly. A three-month pre-post quasi-experimental study involved 53 community-dwelling adults aged ≥70 years in Sherbrooke, Quebec. Participants took 1200 µg/day of vitamin B12 supplements for three months and provided four monthly fasting urine samples to enable analysis of the urinary MA/creatinine ratio before, during and after supplementation. Balance (Berg Balance Scale, ABC Scale), cognitive function (MoCA) and nerve conduction (transcranial magnetic stimulation) were assessed at baseline and after intervention. A significant reduction in uMMA levels was observed after supplementation (1.36 to 1.10, p < 0.001), with improvements in cognitive performance (MoCA, p = 0.017) and balance (BBS, p < 0.001). However, no statistically significant changes were found in nerve conduction. A significant correlation was found between the reduction in uMMA/creatinine ratio and cognitive improvement (r = 0.318, p < 0.05). Urinary methylmalonic acid is a promising biomarker for assessing vitamin B12 deficiency and monitoring response to treatment in the elderly. Further, more in-depth studies over a longer period of supplementation are needed to confirm its clinical utility in this population and to better assess the impact on neurophysiological outcomes and confirm cognitive and balance measures.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".