Clinical practice. Vitamin B12 deficiency.

Division of Hematology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
New England Journal of Medicine (Impact Factor: 54.42). 01/2013; 368(2):149-60. DOI: 10.1056/NEJMcp1113996
Source: PubMed
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    01/2015; 24(1). DOI:10.1016/j.jpge.2014.08.001
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    ABSTRACT: Emerging evidence indicates an association between obesity, metformin use and reduced vitamin B12 status, which can have serious hematologic, neurologic and psychiatric consequences. This study aimed to examine B12 status in obese adolescents with pre-diabetes and/or clinical features of insulin resistance. Serum B12 was measured using chemiluminescence immunoassay in 103 (43 male, 60 female) obese (mean body mass index (BMI) z-score ± SD (2.36 ± 0.29)), adolescents aged 10 to 17 years, median (range) insulin sensitivity index of 1.27 (0.27 to 3.38) and 13.6% had pre-diabetes. Low B12 (<148 pmol/L) was identified in eight (7.8%) and borderline status (148 to 221 pmol/L) in an additional 25 (24.3%) adolescents. Adolescents with borderline B12 concentrations had higher BMI z-scores compared to those with normal concentrations (2.50 ± 0.22 vs. 2.32 ± 0.30, p = 0.008) or those with low B12 concentration (2.50 ± 0.22 vs. 2.27 ± 0.226, p = 0.041). In conclusion, nearly a third of obese adolescents with clinical insulin resistance had a low or borderline serum B12 status. Therefore, further investigations are warranted to explore the cause and the impact of low B12 status in obese pediatric populations.
    Nutrients 01/2014; 6(12):5611-5618. DOI:10.3390/nu6125611 · 3.15 Impact Factor
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    ABSTRACT: Myeloproliferative disorders are characterized by proliferation of 1 or more lineage of hematologic cells. Rapid proliferation of cells may lead to depletion of vitamin B12, which may be falsely elevated by conventional assays in these disorders. We evaluated vitamin B12 status with conventional vitamin B12 assay and levels of serum methylmalonic acid (MMA), serum holotranscobalamin (holoTC), and plasma homocysteine in myeloproliferative disorders. In 58 patients who had myeloproliferative disorders and normal serum creatinine levels, we measured levels of vitamin B12, MMA, holoTC, and homocysteine. Correlations were evaluated between these tests, with MMA as the reference standard for vitamin B12 deficiency. Prevalence of vitamin B12 deficiency was 69%, despite high serum vitamin B12 levels. Levels of holoTC of 40.6 pmol/L or less and homocysteine of greater than 14 mol/L were the best cutoff levels with sensitivity values of 75% and 70%, specificity values of 80% and 68%, and positive predictive values of 88% and 80%. Logistic regression showed that cutoff values of holoTC of 40.6 pmol/L or less and homocysteine of greater than 14 mol/L resulted in odds ratio 15.5 for low versus high holoTC, and odds ratio 5.4 for high versus low homocysteine, to confirm vitamin B12 deficiency. Patients who had myeloproliferative disorders had a high prevalence of vitamin B12 deficiency, despite high serum vitamin B12 levels. Therefore, vitamin B12 status should be evaluated in patients with myeloproliferative disorders. Holotranscobalamin level may be the best initial test and may replace vitamin B12 assay to accompany MMA and homocysteine levels.