Article

Vitamin B12 Deficiency

U.S. Army Health Clinic, Darmstadt, Germany.
American family physician (Impact Factor: 2.18). 04/2003; 67(5):979-86.
Source: PubMed

ABSTRACT

Vitamin B12 (cobalamin) deficiency is a common cause of macrocytic anemia and has been implicated in a spectrum of neuropsychiatric disorders. The role of B12 deficiency in hyperhomocysteinemia and the promotion of atherosclerosis is only now being explored. Diagnosis of vitamin B12 deficiency is typically based on measurement of serum vitamin B12 levels; however, about 50 percent of patients with subclinical disease have normal B12 levels. A more sensitive method of screening for vitamin B12 deficiency is measurement of serum methylmalonic acid and homocysteine levels, which are increased early in vitamin B12 deficiency. Use of the Schilling test for detection of pernicious anemia has been supplanted for the most part by serologic testing for parietal cell and intrinsic factor antibodies. Contrary to prevailing medical practice, studies show that supplementation with oral vitamin B12 is a safe and effective treatment for the B12 deficiency state. Even when intrinsic factor is not present to aid in the absorption of vitamin B12 (pernicious anemia) or in other diseases that affect the usual absorption sites in the terminal ileum, oral therapy remains effective.

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    • "Therefore, MMA is clearly more specific to vitamin B-12 deficiency compared to HC. A deficiency of vitamin B-12 at the tissue level can lead to elevation of both MMA and HC[1]even when serum vitamin B- 12 concentrations are within the reference values. Elevated MMA and HC levels together have been found to be 99.8% sensitive for diagnosing functional vitamin B-12 deficiency[10], which is defined as elevated MMA and HC levels despite normal vitamin B-12 levels in asymptomatic individuals111213. "
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    ABSTRACT: Background/aims: Normal or high serum vitamin B-12 levels can sometimes be seen in a B-12 deficient state, and can therefore be misleading. High levels of Methymalonic Acid (MMA) and Homocysteine (HC) have been identified as better indicators of B-12 deficiency than the actual serum B-12 level itself. We evaluated the prevalence of vitamin B-12 deficiency using appropriate cut-off levels of vitamin B-12, MMA and HC, and determined the relationship between serum levels of vitamin B-12, MMA and HC in cancer. Methods: This is a cross-sectional study using a consecutive case series of 316 cancer patients first seen at Cancer Treatment Centers of America® (CTCA) at Midwestern Regional Medical Center between April 2014 and June 2014. All patients were evaluated at baseline for vitamin B-12 (pg/mL), MMA (nmol/L) and HC (μmol/L) levels. In accordance with previously published research, the following cut-offs were used to define vitamin B-12 deficiency: <300 pg/mL for vitamin B-12, >260 nmol/L for MMA and >12 μmol/L for HC. The relationship between B-12, MMA and HC was evaluated using Spearman's rho correlation coefficient and cross-tabulation analysis. Receiver Operating Characteristic (ROC) curves were estimated using the non-parametric method to further evaluate the diagnostic accuracy of vitamin B-12 using Fedosov quotient as the "gold standard". Results: Mean age at presentation was 52.5 years. 134 (42.4%) patients were males while 182 (57.6%) were females. Median vitamin B-12, MMA and HC levels were 582.5 pg/mL, 146.5 nmol/L and 8.4 μmol/L respectively. Of 316 patients, 28 (8.9%) were vitamin B-12 deficient based on vitamin B-12 (<300pg/mL), 34 (10.8%) were deficient based on MMA (>260 nmol/L) while 55 (17.4%) were deficient based on HC (>12 μmol/L). Correlation analysis revealed a significant weak negative correlation between vitamin B-12 and MMA (rho = -0.22) as well as B-12 and HC (rho = -0.35). ROC curves suggested MMA to have the best discriminatory power in predicting B-12 deficiency. Conclusion: Vitamin B-12 is poorly correlated with MMA and HC in cancer. Using serum vitamin B-12 alone to evaluate B-12 status in cancer may fail to identify those with functional deficiency. A thorough clinical assessment is important to identify patients that may have risk factors and/or symptoms suggestive of deficiency. These patients should have additional testing of MMA and HC regardless of their B-12 levels.
    Full-text · Article · Jan 2016 · PLoS ONE
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    • "The human body requires vitamin B 12 in order to maintain a variety of processes vital to health and maintenance among which are cell reproduction and growth, and nucleoprotein and myelin synthesis [5]. In the nervous system, vitamin B 12 plays a role in nerve metabolism via the remethylation of homocysteine to methionine for de novo synthesis of sadenosylmethionine [6]. One of the mechanisms believed to be at play in vitamin B 12 deficiency neuropathy is hypomethylation in the central nervous system. "

    Full-text · Article · Nov 2015 · International Journal of Scientific & Technology Research
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    • "The human body requires vitamin B 12 in order to maintain a variety of processes vital to health and maintenance among which are cell reproduction and growth, and nucleoprotein and myelin synthesis [5]. In the nervous system, vitamin B 12 plays a role in nerve metabolism via the remethylation of homocysteine to methionine for de novo synthesis of sadenosylmethionine [6]. One of the mechanisms believed to be at play in vitamin B 12 deficiency neuropathy is hypomethylation in the central nervous system. "

    Full-text · Article · Nov 2015 · International Journal of Scientific & Technology Research
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