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- Clarke, Robert, et al.
(author)
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Detection of vitamin B12 deficiency in older people by measuring vitamin B12 or the active fraction of vitamin B12, holotranscobalamin.
- 2007
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In: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 53:5, s. 963-970
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Journal article (peer-reviewed)abstract
- BACKGROUND: Impaired vitamin B(12) function and decreased vitamin B(12) status have been associated with neurological and cognitive impairment. Current assays analyze total vitamin B(12) concentration, only a small percentage of which is metabolically active. Concentrations of this active component, carried on holotranscobalamin (holoTC), may be of greater relevance than total vitamin B(12). METHODS: We compared the utility of serum holoTC with conventional vitamin B(12) for detection of vitamin B(12) deficiency in a population-based study of older people, using increased methylmalonic acid (MMA) concentrations as a marker of metabolic vitamin B(12) deficiency in the overall population (n = 2403) and in subsets with normal (n = 1651) and abnormal (n = 752) renal function. RESULTS: Among all participants, 6% had definite (MMA >0.75 micromol/L) and 16% had probable (MMA >0.45 micromol/L) metabolic vitamin B(12) deficiency. In receiver operating characteristic curves for detection of definite vitamin B(12) deficiency, holoTC had a greater area under the curve (AUC) compared with vitamin B(12) in all participants (0.85 vs 0.76; P <0.001) and in subsets with normal (AUC: 0.87 vs 0.79; P <0.001) and abnormal (AUC: 0.85 vs 0.74; P = 0.002) renal function. Similar findings were observed for detection of moderate vitamin B(12) deficiency. Whereas the positive predictive value for both holoTC and vitamin B(12) was greater for detection of probable than definite vitamin B(12) deficiency, both tests were associated with more false-positive than true-positive test results. CONCLUSIONS: HoloTC has a modestly superior diagnostic accuracy compared with conventional vitamin B(12) for the detection of vitamin B(12) deficiency, but neither test can be recommended to screen asymptomatic populations.
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- Hin, Harold, et al.
(author)
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Clinical relevance of low serum vitamin B12 concentrations in older people : the Banbury B12 study
- 2006
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In: Age and Ageing. - London : Oxford University Press. - 0002-0729 .- 1468-2834. ; 35:4, s. 416-422
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Journal article (peer-reviewed)abstract
- Background: low vitamin B12 concentrations are common in older people, but the clinical relevance of biochemical evidence of vitamin B12 deficiency in the absence of anaemia is uncertain. Objective: to examine associations of cognitive impairment, depression and neuropathy with blood measurements of vitamin B12 and folate status in older people. Design: cross-sectional study in general practice in Banbury, England. Participants: a total of 1,000 individuals aged 75 years or older living in the community. Results: low vitamin B12 concentrations were identified in 13% of older people and were associated with memory impairment and depression. After adjustment for age, sex and smoking, individuals with vitamin B12 or holotranscobalamin (holoTC) in the bottom compared with top quartiles had a 2-fold risk (OR = 2.17; 95% CI 1.11-4.27) and a 3-fold risk (OR = 3.02; 95% CI 1.31-6.98) of cognitive impairment, respectively. Low vitamin B12 status was also associated with missing ankle tendon jerks but not with depression. Treatment with vitamin B12 for 3 months corrected the biochemical abnormalities but had no effect on any of the clinical measurements. Conclusions: low vitamin B12 concentrations are associated with cognitive impairment and missing ankle tendon jerks in older people in the absence of anaemia. Large-scale trials of vitamin B12 supplementation are required to assess the clinical significance of these associations.
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