High serum cobalamin levels in the clinical setting--clinical associations and holo-transcobalamin changes

Just a vitamin? Should cobalamin (Vitamin B12) levels be checked in children with neurological disadvantages?

OBJECTIVE

The assay of serum cobalamin (Cbl) level is commonly used to diagnose Cbl deficiency. Unexpectedly, the elevated Cbl levels may be determined in some of the patients and its interpretation is difficult. We investigated the association between elevated Cbl levels and a variety of clinical entities in patients presenting with various neurological symptoms.

METHODS

The data were obtained from the patients' electronic medical records in a tertiary hospital affiliated with a university. The pediatric patients with serum Cbl levels above 1000 pg/mL were included in the study. The patients with serum Cbl levels below 900 pg/mL and above 200 pg/mL constituted the control group.

RESULTS

The mean Cbl level of the patients with neurological problems was 1424.2±354.2 pg/mL, whereas the average Cbl level of neurologically healthy was 1316±317.8 pg/mL, and the difference was statistically significant. While the rate of having neurological deficits or symptoms in the study group was found to be 24%, this rate was only 18% in the control group. Unexpectedly, despite elevated Cbl level, the high mean corpuscular volume rate was higher in the study group compared to the control group.

CONCLUSION

This study highlights the importance of the disorders of Cbl metabolism in patients presenting with various neurological symptoms. In children with neurological deficits, serum Cbl levels should be checked. In case of high Cbl level is determined, patients should be followed up closely, and further investigations should be performed in terms of Cbl metabolism disorders.

Etiology of Anemia and Risk Factors of Mortality among Hospitalized Patients: A Real-Life Retrospective Study in a Tertiary Center in Greece

Anemia is a prominent global health issue with a wide variety of causes and can be associated with decreased quality of life, increased hospitalization, and higher mortality, especially in older individuals. Therefore, studies further shedding light on the causes and the risk factors of this condition should be performed. The aim of the present study was to examine the causes of anemia in hospitalized patients in a tertiary hospital in Greece and identify risk factors related to higher mortality. In total, 846 adult patients with a diagnosis of anemia were admitted during the study period. The median age was 81 years, and 44.8% were male. The majority of patients had microcytic anemia, with the median mean corpuscular volume (MCV) being 76.3 fL and the median hemoglobin being 7.1 g/dL. Antiplatelets were used by 28.6% of patients, while 28.4% were using anticoagulants at the time of diagnosis. At least one unit of packed red blood cells (PRBCs) was transfused in 84.6% of patients, and a median of two PRBCs was used per patient. A gastroscopy was performed in 55%, and a colonoscopy was performed in 39.8% of patients in the present cohort. Anemia was considered to be multifactorial in almost half the cases, while the most commonly identified cause was iron deficiency anemia, more commonly with positive endoscopic findings. Mortality was relatively low, at 4.1%. Multivariate logistic regression analysis identified higher B12 levels and longer duration of hospital stay to be independently positively associated with mortality.

Age- and ethnicity-related reference intervals for serum vitamin B12

BACKGROUND

Age and ethnicity are known to influence serum vitamin B₁₂ (B₁₂) concentration, yet universal reference intervals (RIs) are typically applied by laboratories. Both lower and upper RI limits for B₁₂ are clinically relevant. Low values suggest deficiency leading to anemia and/or neurological impairment, while high values are not always an innocuous consequence of high B₁₂ intake but are associated with some cancers, autoimmune, liver, and renal diseases. This work aimed to establish age- and ethnicity-related RIs for B₁₂ using a modified indirect method based on Hoffmann's approach.

METHODS

A total of 72,091 anonymized B₁₂ results (Jan 2018-Nov 2019) were analyzed from an ethnically-diverse South-East London general practice patient population. Patients belonged to five ethnic groups: Asian, Black, White, Mixed, or Other. Multiple records for the same patient and results with missing ethnicity were excluded from the analysis of adult RIs. B₁₂ analyses were performed using ARCHITECT® (Abbott Diagnostics).

RESULTS

B₁₂ was significantly higher in Black compared with Asian and White adults. There were no differences in B₁₂ between Asian and White adults. Children (all ethnicities) between 2 and 5 years old had the highest B₁₂. Because of the small number of children (up to the age of 13) in each ethnic-related age category, all ethnic groups were combined to obtain age-related RIs. The children's RIs ranged from 159 to 1025 pmol/L for 0-1-year-olds to 276-1102 pmol/L for 2-5-year-olds. The RIs for Black and White/Asian people >13 years of age were 166-805 pmol/L and 134-511 pmol/L respectively.

CONCLUSIONS

The application of age- and ethnicity-appropriate RIs into diagnostic practice will provide a more accurate evaluation of B₁₂ status when using the B₁₂ test alone or in combination with other markers.

"Macro transcobalamin causing raised vitamin B12: Case-based laboratory investigation"

Determination of plasma vitamin B12 (B12) is a frequently requested laboratory analysis, mainly employed to establish B12 deficiency. However, an increased level of B12 is a common unexpected finding that may be related to an increased concentration of one of the B12 binding proteins, haptocorrin or transcobalamin. This paper describes the extensive laboratory evaluation of a patient with an elevated level of plasma B12 with various well-established assays. Initial studies suggested the presence of a macromolecule consisting of haptocorrin bound B12. Specific determinations of the B12-binding proteins revealed normal amounts of haptocorrin but a markedly increase in both total and B12 saturated transcobalamin (holo-TC). The results are in accord with the presence of macro-transcobalamin. These experiments reveal that determination of the nature of the B12-macromolecules is troublesome due to differences in assays applied to measure these proteins. In addition, this publication creates awareness of macro-holo-TC as a cause of an unexplained increased B12 level.

Pernicious anemia: Pathophysiology and diagnostic difficulties

Pernicious anemia (PA) is the most common cause of vitamin B12 (cobalamin) deficiency anemia in the world. It is an autoimmune disease, comprising of salient features of autoimmune chronic atrophic gastritis (CAG) and cobalamin deficiency (CD). Although the anemia was first described as pernicious, it may well be controlled with vitamin B12 replacement. The onset and progression of PA is often insidious. Alternatively, patients may have no anemic symptoms since they become acclimatized to the subtle nature of the disease. Oftentimes, there is a possibility that the underlying disease may be missed unless a full blood count (FBC) is investigated, leading to hindrance in the treatment journey. Diagnostic challenges remain tangible for many practicing clinicians, since there is lack of reliable cobalamin assays to diagnose CD as well as clinical mimics, which simulate many other hematological conditions, such as myelodysplastic syndrome, acute leukemia, sideroblastic anemias, bone marrow failure states, thrombotic microangiopathy, and thromboembolism. Moreover, prompt recognition of the symptoms of CD is also vital, because some neurologic sequalae may become irreversible despite replenishing cobalamin. Herein, we discuss a literature review on the pathophysiology, challenging clinical presentations and diagnostic difficulties of PA. Since the cobalamin replacement therapy for PA is straightforward, it will not be discussed in this review.

Macro vitamin B12: an underestimated threat

Background The correct identification of the macro-B12 interference (macroforms) is paramount to avoid potential erroneous clinical decisions. Our objectives were to determine whether immunoassays are affected by the presence of macro-B12 and to validate a polyethylene glycol (PEG) precipitation procedure to detect it. Methods Sixty-two serum samples obtained from healthy volunteers were analyzed to determine recovery and reference intervals (RIs) following PEG precipitation. Thereafter, 50 serum samples with very high levels of B12 (>1476 pmol/L) were randomly selected to search for macro-B12 interferences. Serum samples obtained from healthy volunteers and related PEG aliquots were analyzed on a Cobas® immunoassay. Patients' samples were analyzed on both Cobas® and Architect® immunoassays. Finally, samples suspected to contain macro-B12 were analyzed by size-exclusion chromatography (SEC) to confirm the presence of macro-B12. Results Recovery and post-PEG RIs determined on a Cobas 8000® in healthy volunteers ranged from 68.3% to 108.4% and from 122.1 to 514.4 pmol/L, respectively. Fifteen samples (30%) were found to show macro-B12 while using the recovery criteria, and nine samples (18%) while using the post-PEG RI. The other immunoassay ran on the Architect i2000® was also affected by the presence of macro-B12. Size-exclusion chromatography studies confirmed the presence of macro-B12 (immunoglobulin-B12 complexes). Conclusions The prevalence of macro-B12 in elevated B12 samples is high. We suggest to systematically screen for the presence of macro-B12 with PEG precipitation procedure in samples with elevated B12 levels to avoid potential misdiagnosis or harmful clinical consequences.

Predictive role of vitamin B12 in acute kidney injury in living donor liver transplantation: a propensity score matching analysis

OBJECTIVES

We examine the association between vitamin B₁₂ level and risk for acute kidney injury (AKI) in patients undergoing living donor liver transplantation (LDLT).

DESIGN

Retrospective observational cohort study.

SETTING

University hospital, from January 2009 to December 2018.

PARTICIPANTS

A total of 591 patients who underwent elective LDLT were analysed in this study. Those with a preoperative history of kidney dysfunction, vitamin B₁₂ supplementation due to alcoholism, low vitamin B₁₂ (<200 pg/mL) or missing laboratory data were excluded.

PRIMARY AND SECONDARY OUTCOME MEASURES

The population was classified into AKI and non-AKI groups according to Kidney Disease Improving Global Outcomes (KDIGO) criteria, and associations between perioperative factors and AKI were analysed. After 1:1 propensity score (PS) matching, the association between high vitamin B₁₂ (>900 pg/mL) and postoperative AKI was evaluated.

RESULTS

Preoperative vitamin B₁₂ was higher in the AKI group. Potentially significant perioperative factors from univariate analyses were entered into multivariate analyses, including preoperative factors (vitamin B₁₂, diabetes), intraoperative factors (hourly urine output) and donor graft fatty change in LDLT patients. PS matching analyses with adjustment using PS revealed that high serum vitamin B₁₂ (>900 pg/mL) was associated with risk for AKI, and the risk was 2.8-fold higher in patients with high vitamin B₁₂ than in those with normal vitamin B₁₂. Higher vitamin B₁₂ was also related to a higher AKI stage. In addition, inflammatory factors (C reactive protein, white blood cells and albumin) were associated with vitamin B₁₂ level.

CONCLUSIONS

Our study may improve the accuracy of predicting postoperative AKI by introducing preoperative vitamin B₁₂ into risk assessments for patients undergoing LDLT.

B Vitamins and One-Carbon Metabolism: Implications in Human Health and Disease

Vitamins B9 (folate) and B12 are essential water-soluble vitamins that play a crucial role in the maintenance of one-carbon metabolism: a set of interconnected biochemical pathways driven by folate and methionine to generate methyl groups for use in DNA synthesis, amino acid homeostasis, antioxidant generation, and epigenetic regulation. Dietary deficiencies in B9 and B12, or genetic polymorphisms that influence the activity of enzymes involved in the folate or methionine cycles, are known to cause developmental defects, impair cognitive function, or block normal blood production. Nutritional deficiencies have historically been treated with dietary supplementation or high-dose parenteral administration that can reverse symptoms in the majority of cases. Elevated levels of these vitamins have more recently been shown to correlate with immune dysfunction, cancer, and increased mortality. Therapies that specifically target one-carbon metabolism are therefore currently being explored for the treatment of immune disorders and cancer. In this review, we will highlight recent studies aimed at elucidating the role of folate, B12, and methionine in one-carbon metabolism during normal cellular processes and in the context of disease progression.

Association of Plasma Concentration of Vitamin B12 With All-Cause Mortality in the General Population in the Netherlands

IMPORTANCE

Higher plasma concentrations of vitamin B12 have been associated with mortality in elderly and hospitalized populations, including patients with chronic kidney disease, but the association of plasma concentrations of vitamin B12 with mortality in the general population remains unclear.

OBJECTIVE

To investigate the association of plasma concentrations of vitamin B12 with all-cause mortality.

DESIGN, SETTING, AND PARTICIPANTS

This longitudinal cohort study used post hoc analysis to examine data from participants of the Prevention of Renal and Vascular End-stage Disease Study in Groningen, the Netherlands. Participants included individuals who completed the second screening visit beginning January 1, 2001, excluding those who were missing values of vitamin B12 plasma concentrations or used vitamin B12 supplementation. Follow-up time was defined between the beginning of the second screening round to end of follow-up on January 1, 2011. Data analysis was conducted from October 2, 2018, to February 22, 2019.

EXPOSURES

Plasma vitamin B12 concentration level.

MAIN OUTCOMES AND MEASURES

Death as recorded by the Central Bureau of Statistics of Groningen, the Netherlands.

RESULTS

A total of 5571 participants (mean [SD] age, 53.5 [12.0] years; 2830 [50.8%] men) were included in analyses. Median (interquartile range) plasma concentration of vitamin B12 was 394.42 (310.38-497.42) pg/mL. During the median (interquartile range) of 8.2 (7.7-8.9) years of follow-up, 226 participants (4.1%) died. According to quartiles of the distribution of plasma vitamin B12 concentration levels, mortality rates were 33.8 deaths per 10 000 person-years for the quartile with the lowest plasma concentration of vitamin B12 and 65.7 deaths per 10 000 person-years for the quartile with the highest plasma concentration of vitamin B12. After adjustment for multiple clinical and laboratory variables, Cox regression analyses found a significant association between higher vitamin B12 plasma concentration level and increased risk of all-cause mortality (hazard ratio per 1-SD increase, 1.25 [95% CI, 1.06-1.47]; P = .006).

CONCLUSIONS AND RELEVANCE

These findings suggest that higher levels of plasma concentrations of vitamin B12 were associated with increased risk of all-cause mortality after adjusting for age, sex, renal function, and other clinical and laboratory variables. The mechanisms underlying this association remain to be established.

Hypervitaminosis B12 - a new marker and predictor of prognostically unfavorable diseases

A high serum vitamin B12 level (hypercobalaminemia) is a underestimated anomaly. Clinically, it can be paradoxically accompanied by signs of deficiency, which are related to defects in tissue uptake of vitamin B12. The increase in the level of serum cobalamin occurs mainly in serious diseases that require early diagnosis: hemoblastosis, liver and kidney diseases, etc. This review presents data on the metabolism of vitamin B12 and the potential significance of increasing its level as a marker for the early diagnosis of these diseases.

Vitamin B12 Intake From Animal Foods, Biomarkers, and Health Aspects

The EAT-Lancet commission recently suggested that transformation to healthy diets by 2050 will require a reduction of at least 50% in consumption of foods such as red meat and sugar, and a doubling in the global consumption of fruits, vegetables, nuts, and legumes. A diet rich in plant-based foods and with fewer animal source foods confers both improved health and environmental benefits. Notably, the risk of vitamin B12 deficiency increases when consuming a diet low in animal products. Humans are dependent on animal foods such as dairy products, meat, fish and eggs. Vitamin B12 deficiency is common worldwide, especially in populations with low consumption of animal foods because of low socioeconomic status, ethical reasons, or because of their lifestyle (i.e., vegans). According to the European Food Safety Authoroty, the recommended adequate intake of vitamin B12 is 4.0 μg/d for adults, and vitamin B12 requirements are higher during pregnancy and lactation. Infants and children from deficient mothers and elderly people are at risk for vitamin B12 deficiency. Diagnosis of vitamin B12 deficiency is hampered by low specificity of available biomarkers, and there is no consensus yet regarding the optimal definition of low vitamin B12 status. In general, a combination of at least two biomarkers is recommended. Therefore, this review presents an overview of vitamin B12 biochemistry and its biomarkers. We further summarize current recommendations of vitamin B12 intake, and evidence on the associations of vitamin B12 intake from different nutrient-dense animal foods with vitamin B12 status markers. Finally, potential consequences of low vitamin B12 status on different health outcomes for pregnant women, infants and elderly are presented.

Association of vitamin D and vitamin B12 with cognitive impairment in elderly aged 80 years or older: a cross-sectional study

BACKGROUND

The present study aimed to assess the association of vitamin D and vitamin B₁₂ with cognitive impairment in elderly people.

METHODS

The data were obtained from a cross-sectional study that included individuals aged 80 years or older living in the urban and rural areas of the cities of Siderópolis and Treviso in the state of Santa Catarina, Brazil. In total, 165 elderly people were included in the analysis. The outcome of cognitive decline was assessed by the Mini-Mental State Examination. Vitamin D and vitamin B₁₂ levels were measured from blood samples. The socio-demographic, anthropometric and health variables used in the analysis were collected from a questionnaire. Crude and adjusted analyses of the relationship between vitamins D and B₁₂ and cognitive decline were performed using a Poisson regression model.

RESULTS

The prevalence of cognitive decline was 35.2%. In the adjusted model, individuals who had vitamin D levels >19 ng mL^-1 showed a lower prevalence of cognitive decline (prevalence ratio = 0.59; 95% confidence interval = 0.39-0.87). Those participants who had vitamin B₁₂ levels of ≥496 pg mL^-1 had a higher prevalence of cognitive decline (prevalence ratio = 1.90; 95% confidence interval = 1.08-3.36).

CONCLUSIONS

The present study showed that individuals aged ≥80 years who had vitamin D levels of ≤18 ng mL^-1 had a higher prevalence of cognitive decline even after adjustment for potential confounders. In addition, the study demonstrated that vitamin B₁₂ levels of ≥496 pg mL^-1 in this population were also a risk factor for cognitive decline. A cross-sectional analysis does not enable the inference of a cause-effect relationship and additional studies are needed to understand these relationships.

Vitamin B12 Deficiency and the Role of Gender: A Cross-Sectional Study of a Large Cohort

Background: Vitamin B12 deficiency is associated with hematological, neurological, and cardiovascular consequences. Epidemiologic data on these related illnesses indicate gender differences. Methods: A cross-sectional study was designed to examine gender differences in vitamin B12 deficiency among a healthy population. Data from healthy individuals aged 18–65, who were provided with a routine medical evaluation during 2000–2014, were retrieved from the medical charts. Individuals with background illnesses and those who had used medications or nutritional supplements were excluded. Vitamin B12 deficiency was defined by 2 cutoff values (206 and 140 pmol/L). The multivariate analysis was adjusted for age, body mass index, estimated glomerular filtration rate, hyperhomocysteinemia, folate deficiency, albumin, and transferrin saturation. Sensitivity analyses were implemented by excluding individuals with anemia, hyperhomocysteinemia, or folate deficiency and by age stratification. Results: In all, 7,963 individuals met the inclusion criteria. Serum vitamin B12 mean levels were 312.36 and 284.31 pmol/L for women and men respectively (p < 0.001). Deficiency prevalence was greater for men (25.5%) in comparison with women (18.9%; p < 0.001). Men were strongly associated with severe deficiency (adjusted OR 2.26; 95% CI 1.43–3.56). Conclusions: Among the healthy population, men are susceptible to vitamin B12 deficiency. This can be explained by neither diet habits nor estrogen effects. Genetic variations are therefore hypothesized to play a role.

[What to do before a hypervitaminia B12 in the elderly]

Hypervitanimia B12 is an early marker of serious pathologies. These include solid neoplasms, malignant blood diseases and acute/chronic hepatopathies. Hypervitaminemia B12 in geriatrics is thereby an indicator in the diagnosis and prognosis of these conditions.

Transcobalamin 776C→G polymorphism is associated with peripheral neuropathy in elderly individuals with high folate intake

BACKGROUND

The 776C→G polymorphism of the vitamin B-12 transport protein transcobalamin gene (TCN2) (rs1801198; Pro259Arg) is associated with a lower holotranscobalamin concentration in plasma. This effect may reduce the availability of vitamin B-12 to tissues even when vitamin B-12 intake is adequate. Clinical outcomes associated with vitamin B-12 insufficiency could potentially be worsened by high folate intake.

OBJECTIVE

We determined the association of the TCN2 776C→G polymorphism and folate intake with peripheral neuropathy in elders with normal plasma concentrations of vitamin B-12.

DESIGN

Participants in this cross-sectional study (n = 171) were from a cohort of community-based, home-bound elderly individuals aged ≥60 y who underwent an evaluation by physicians including an assessment for peripheral neuropathy. Participants were administered food-frequency and general health status questionnaires, anthropometric measurements were taken, and a fasting blood sample from each subject was collected.

RESULTS

Odds of neuropathy were 3-fold higher for GG genotypes than for CC genotypes (OR: 3.33; 95% CI: 1.15, 9.64). When folate intake was >2 times the Recommended Dietary Allowance (800 μg), GG genotypes had 6.9-fold higher odds of neuropathy than CC genotypes (OR: 6.9; 95% CI: 1.31, 36.36). There was no difference between the genotypes in the odds of peripheral neuropathy when folate intake was ≤800 μg (OR: 1.5; 95% CI: 0.18, 12.33).

CONCLUSION

The TCN2 776C→G polymorphism is associated with increased odds of peripheral neuropathy in the elderly, even with a normal vitamin B-12 status, especially if their folate intake is >2 times the Recommended Dietary Allowance.

Elevated plasma vitamin B12 levels and cancer prognosis: A population-based cohort study

BACKGROUND

Elevated plasma vitamin B12 levels (cobalamin, Cbl) are associated with increased short-term cancer risk among patients referred for this laboratory measurement. We aimed to assess prognosis in cancer patients with elevated plasma Cbl.

METHODS

We conducted a population-based cohort study using data from Danish medical registries during 1998-2014. The study included 25,017 patients with a cancer diagnosis and Cbl levels of 200-600 pmol/L (reference/normal range), 601-800 pmol/L and >800 pmol/L measured up to one year prior to diagnosis, and a comparison cohort of 61,988 cancer patients without a plasma Cbl measurement. Patients treated with Cbl were excluded. Survival probability was assessed using Kaplan-Meier curves. Mortality risk ratios (MRR) were computed using Cox proportional hazard regression, adjusted for age, sex, calendar year, cancer stage and comorbidity, scored using the Charlson comorbidity index.

RESULTS

Survival probabilities were lower among patients with elevated Cbl levels than among patients with normal levels and among members of the comparison cohort [(1-year survival,%) Cbl: 200-600 pmol/L: 69.3%; 601-800 pmol/L: 49.6%; >800 pmol/L: 35.8%; comparison cohort: 72.6%]. Thirty-day mortality was elevated for patients with Cbl levels of 601-800 pmol/L or >800 pmol/L, compared to patients with levels of 200-600 pmol/L [(MRR (95% confidence interval): 601-800 pmol/L vs. 200-600 pmol/L: 1.9 (1.6-2.2); >800 pmol/L vs. 200-600 pmol/L: 2.7 (2.4-3.1)]. This association remained robust for 31-90-day and 91-365-day mortality, showing similar dose-response patterns.

CONCLUSION

Cancer patients with elevated Cbl levels had higher mortality than those with normal Cbl levels. These findings may have clinical significance for assessing the prognosis of cancer patients.

Autoimmune mechanisms in pernicious anaemia & thyroid disease

Pernicious anaemia (PA) and some types of thyroid disease result from autoimmune processes. The autoimmune mechanisms in these conditions have not been fully elucidated. This review discusses the autoimmune mechanisms involved in PA and how these affect diagnosis and disease progression. In addition to gastric antibodies, antibodies to the vitamin B12 binding protein transcobalamin which can result in high serum B12 levels are also addressed with regard to how they affect clinical practice. The role of autoimmune susceptibility is investigated by comparing PA to one of its most common comorbidities, autoimmune thyroid disease (AITD). Thyroid disease (although not exclusively AITD) and B12 deficiency are both also implicated in the pathology of hyperhomocysteinemia, an elevated homocysteine in plasma. Since hyperhomocysteinemia is a risk factor for cardiovascular occlusive disease, this review also addresses how thyroid disease in particular leads to changes in homocysteine levels.

The association between vitamin B12, albuminuria and reduced kidney function: an observational cohort study

Background

Variants in CUBN, the gene encoding cubilin, a proximal tubular transport protein, have been associated with albuminuria and vitamin B12 (B12) deficiency. We hypothesized that low levels of B12 would be associated with albuminuria in a population-based cohort.

Methods

We analyzed participants from the Framingham Heart Study (n = 2965, mean age 58 years, 53% female) who provided samples for plasma B12. Logistic regression models adjusted for covariates including homocysteine were constructed to test the association between B12 and prevalent albuminuria (UACR ≥17 mg/g [men] and ≥25 mg/g [women]) and reduced kidney function (defined as an eGFR < 60 ml/min/1.73 m², RKF). Because of a significant interaction between B12 and homocysteine in the prevalent RKF model (p = 0.005), the model was stratified by the median homocysteine levels. Logistic regression models were constructed to test the association between B12 and incident albuminuria and RKF. The results were replicated in 4445 participants from NHANES 2003–2004.

Results

Baseline B12 levels ranged from 50-1690 pg/ml. Elevated B12 was associated with prevalent albuminuria (OR 1.44 per 1 SD increase, 95% CI 1.10-1.87) and RKF (OR 1.83, 95% CI 1.30-2.60). However after stratifying by median homocysteine levels, this relationship remained only in the higher homocysteine stratum. There was no association between B12 and incident albuminuria (OR 1.17, 95% CI 0.79 – 1.73) or RKF (OR 1.45, 95% CI 0.97 – 1.88). In the NHANES cohort, elevated B12 was associated with RKF after full covariate adjustment (OR 3.06, 95% CI 2.30-4.08). There was no association with albuminuria.

Conclusion

In participants with high baseline homocysteine levels, increased plasma B12 was associated with RKF.

Hypercobalaminaemia is associated with hepatic and neoplastic disease in cats: a cross sectional study

Background

When increased serum cobalamin concentrations are encountered clinically they are usually attributed to parenteral supplementation, dietary factors, or otherwise ignored. However, recently, hypercobalaminaemia has been associated with numerous diseases in humans, most notably neoplastic and hepatic disorders. The aim of this retrospective, observational, cross-sectional study was to determine the significance of increased cobalamin in cats.

Results

In total, 237 records were retrieved and 174 cats, of various ages and sexes met the inclusion criteria. A total of 42 cats had increased serum cobalamin concentration, and had not received prior supplementation. Multiple logistic regression analysis revealed that increased serum cobalamin concentration was positively related to pedigree breed (pedigree breeds more likely to have increased cobalamin concentration, odds ratio [OR] 4.24, 95% CI 1.78-10.15, P = 0.001), to having liver disease (OR 9.91, 95% CI 3.54-27.68), and to having a solid neoplasm (OR 8.54, 95% CI 1.10-66.45).

Conclusions

The results of the current study suggest that increased serum cobalamin concentrations should not be ignored in cats with no history of supplementation, and investigation for underlying hepatic or neoplastic disease is warranted.

Elevated plasma vitamin B12 levels as a marker for cancer: a population-based cohort study

BACKGROUND

A substantial proportion of patients referred for plasma vitamin B12 (cobalamin [Cbl]) measurement present with high Cbl levels, which have been reported in patients with different cancer types. However, the cancer risk among patients with newly diagnosed high Cbl levels has not been adequately examined.

METHODS

We conducted this cohort study using population-based Danish medical registries. Patients referred for Cbl measurement with levels greater than the lower reference limit (≥200 pmol/L) were identified from the population of Northern Denmark during the period of 1998 to 2009 using a database of laboratory test results covering the entire population. Data on cancer incidence (follow-up 1998-2010), Cbl treatment, and prior diagnoses were obtained from medical registries. Patients receiving Cbl treatment were excluded. Cancer risks were calculated as standardized incidence ratios (SIRs) with 95% confidence intervals (CIs), stratified by plasma Cbl levels. All statistical tests were two-sided.

RESULTS

We identified 333 667 persons without prevalent cancer and not receiving Cbl treatment. Six percent had Cbl levels greater than the upper reference limit (≥601 pmol/L). Cancer risk increased with higher Cbl levels and was highest during the first year of follow-up (Cbl 601-800 pmol/L: SIR = 3.44, 95% CI = 3.14 to 3.76; Cbl >800 pmol/L: SIR = 6.27, 95% CI = 5.70 to 6.88; both P < .001). The risks were particularly elevated for hematological and smoking- and alcohol-related cancers for persons with high Cbl levels.

CONCLUSIONS

High Cbl levels were associated with the risk of subsequently diagnosed cancer, mostly within the first year of follow-up. This may have clinical implications for the interpretation of high Cbl levels.

Three family members with elevated plasma cobalamin, transcobalamin and soluble transcobalamin receptor (sCD320)

BACKGROUND

Plasma cobalamin is requested in order to diagnose cobalamin deficiency and low levels confirm a deficient state. Here, we present three family members with unexpected high levels of cobalamin.

METHODS

We included a patient referred for cobalamin measurement due to neurological symptoms, her son and her daughter. Mother and son both suffered from myotonic dystrophy type II, while the daughter tested negative for this disease. Blood samples were analyzed for cobalamin, haptocorrin, transcobalamin, holoTC, and sCD320. We employed gel filtration and antibody precipitation for further characterization. The protein coding region of the TCN2 gene, encoding transcobalamin, was sequenced.

RESULTS

The patient, her {son} and [daughter] all had cobalamin levels above the measurement range of the routine method employed (>1476 pmol/L). Total transcobalamin and (holoTC) were 5980 (1500), {5260 (2410)} and [5630 (1340)] pmol/L, which is well above the upper reference limits of 1500 (160) pmol/L. The sCD320 concentration was also well above the upper reference limit of 97 arb.u.: 1340, {1510} and [1090] arb.u. Haptocorrin levels were within the reference range and no signs of cobalamin deficiency were found. DNA sequencing of the TCN2 gene revealed several known polymorphisms not associated with highly elevated transcobalamin levels. Upon gel filtration, sCD320 eluted as a larger molecule than previously reported. By incubation with anti-transcobalamin antibodies, we precipitated both transcobalamin and part of sCD320.

CONCLUSIONS

The high cobalamin levels were mainly explained by high levels of holoTC, possibly caused by complex formation with its soluble receptor, sCD320. The family occurrence points to a genetic explanation.

Unexpected high plasma cobalamin : proposal for a diagnostic strategy

It is well-established that more than 8% of patients examined for vitamin B12 deficiency unexpectedly have increased plasma levels of the vitamin, but so far there are no guidelines for the clinical interpretation of such findings. In this review, we summarise known associations between high plasma cobalamin and diseases. We report associations mainly with cancer, liver and kidney diseases, but also with a number of other diagnostic entities. The pathogenic background is poorly understood and is likely to be multi-factorial, involving increased concentrations of one or both of the circulating cobalamin binding proteins, transcobalamin and haptocorrin. Based on current knowledge, we suggest a strategy for the clinical interpretation of unexpected high plasma cobalamin. Since a number of the associated diseases are critical and life-threatening, the strategy promotes the concept of 'think the worst first'. It is important to realise that high cobalamin levels can be an unspecific marker for cancer. If this can be ruled out, diseases of the liver and kidney should be considered.

Cancer incidence in persons with elevated cobalamin levels

BACKGROUND

Elevated cobalamin level (ECL) is an epiphenomenon for several cancer types. The clinical significance of ECL at routine testing is, however, unknown. The aim of this study was to examine cancer incidences among persons with ECL.

DESIGN

In a cohort study, Funen County residents (inhabitants 476,580), Denmark, without cancer or injected cobalamin prescriptions were followed from first cobalamin measurement during 1999-2009. Follow-up was stratified according to age, gender, and whether the cobalamin level was elevated (> 1,200 pmol/L). Data from national registers on age-specific incidence of cancer in the general population were used to calculate standardised morbidity ratio (SMR).

RESULTS

A total of 490 persons with ECL and 40,104 with non-ECL were followed. Median age was 61 [IQR 44-77] years. Average follow-up was 2.0 years for ECL subjects and 2.7 years for non-ECL subjects. Cancer was diagnosed within the first 6 months of follow-up in 6.7% (CI 4.7-9.3) of ECL subjects and 2.6% (CI 2.4-2.7) of non-ECL subjects. In ECL and non-ECL subjects, SMR for cancer diagnoses were 15.1 (CI 10.4-21.2) and 5.0 (CI 4.7-5.3) within the first 6 months and 3.7 (CI 1.4-8.1) and 1.8 (CI 1.6-2.0) in the following six-month interval. Review of medical records revealed a suspicion of cancer or performance of relevant diagnostic tests in 87% at the time of cobalamin measurement.

CONCLUSIONS

Persons with ECL have a high incidence of cancer partly explained by the reasons for measuring cobalamin. It remains to be determined whether accidentally found ECL would justify a search for cancers.

The pathophysiology of elevated vitamin B12 in clinical practice

Hypercobalaminemia (high serum vitamin B12 levels) is a frequent and underestimated anomaly. Clinically, it can be paradoxically accompanied by signs of deficiency, reflecting a functional deficiency linked to qualitative abnormalities, which are related to defects in tissue uptake and action of vitamin B12. The aetiological profile of high serum cobalamin predominantly encompasses severe disease entities for which early diagnosis is critical for prognosis. These entities are essentially comprised of solid neoplasms, haematological malignancies and liver and kidney diseases. This review reflects the potential importance of the vitamin B12 assay as an early diagnostic marker of these diseases. A codified approach is needed to determine the potential indications of a search for high serum cobalamin and the practical clinical strategy to adopt upon discovery of elevated cobalamin levels. While low serum cobalamin levels do not necessarily imply deficiency, an abnormally high serum cobalamin level forms a warning sign requiring exclusion of a number of serious underlying pathologies. Functional cobalamin deficiency can thus occur at any serum level.

Altered folate receptor 2 expression in uraemic patients on haemodialysis: implications for folate resistance

BACKGROUND

Folate therapy reduces, but does not normalize homocysteine (Hcy) levels, frequently elevated in chronic kidney disease (CKD). The mechanisms of this folate resistance are unknown. Cellular acquisition of folate is mediated by folate receptors (FRs), whose expression is also modulated by folate status, through an Hcy-dependent regulation mechanism involving heterogeneous nuclear ribonucleoprotein-E1 (hnRNP-E1). Our objective was to evaluate whether an alteration of the FR2 (the form present in nucleated blood cells) expression is present in CKD patients on haemodialysis (HD), and its susceptibility to folate treatment.

METHODS

A population of chronic uraemic patients on HD was enrolled, along with a control group, and studies on FR2 receptor expression and related items were performed in plasma and mononuclear cells from peripheral blood. A subgroup of patients was treated with methyltetrahydrofolate for 1 month.

RESULTS

In HD, there was a significant reduction in FR2 protein expression compared with controls, not correlated with Hcy concentrations, while its mRNA levels were significantly increased. After folate treatment, there was a significant mRNA decrease, in the absence of significant changes in receptor protein expression. hnRNP-E1 gene and protein expression levels increased pre-treatment, while decreased post-treatment.

CONCLUSIONS

In HD, FR2 expression is altered in peripheral mononuclear cells, since its levels are decreased and are not responsive to variations in Hcy concentration, while the intracellular machinery (receptor mRNA and hnRNP-E1), possibly triggering its regulation, is conserved. These findings provide insight into the mechanisms of folate resistance in uraemia.

Cobalamin related parameters and disease patterns in patients with increased serum cobalamin levels

Background

Measurement of serum cobalamin levels is routinely used to diagnose cobalamin deficiency. Surprisingly, approximately 15% of patients have high cobalamin levels and no consensus exists regarding the clinical implications.

Methods

Hospital-treated patients above 18 years of age referred for serum cobalamin measurement were included in groups of patients [percentage cobalamin supplemented] with low (<200 pmol/L, n = 200 [6%]), normal (200–600, n = 202 [6%]) high (601–1000, n = 217 [27%]) and very high (>1000, n = 199 [53%]) cobalamin levels. Total and cobalamin-saturated (holo) transcobalamin, total haptocorrin, soluble TC receptor, sCD320, and methylmalonic acid were analyzed. Data on diagnoses and medical prescriptions was obtained through medical files and the Aarhus University Prescription Database.

Results

Among patients not cobalamin supplemented median total haptocorrin and holo transcobalamin levels were markedly higher in the groups with high/very high cobalamin levels compared to groups with low/normal cobalamin levels. Median total transcobalamin and sCD320 levels were similar across the groups. A number of diagnoses were significantly associated to very high Cbl levels (odds ratio (95% confidence interval)): alcoholism (5.74 (2.76–11.96)), liver disease (8.53 (3.59–20.23)), and cancer (5.48 (2.85–10.55)). Elevated haptocorrin levels were seen in patients with alcoholism, cancer, liver-, renal-, autoimmune-, and bronchopulmonary disease. No clinical associations to sCD320 and total and holo transcobalamin levels were found.

Conclusion

In non-supplemented patients, high cobalamin levels were associated to high haptocorrin levels, and several diagnoses, including alcoholism, liver disease and cancer. Our study emphasizes that clinicians should take high serum cobalamin levels into consideration in the diagnostic process.

Vitamin B-12 and folate status in relation to decline in scores on the mini-mental state examination in the framingham heart study

OBJECTIVES

To investigate the cognitive significance of low to low-normal plasma vitamin B-12 concentrations and to shed light on the role that folate status plays in the association between vitamin B-12 status and cognitive decline.

DESIGN

Associations between plasma vitamin B-12 and folate and 8-year cognitive decline were evaluated, and the effects of interactions between vitamin B-12 status and folate status and supplemental folate use on cognitive decline were assessed.

SETTING

The Framingham Heart Study - a prospective epidemiological study.

PARTICIPANTS

Five hundred forty-nine community-dwelling individuals aged 74.8 ± 4.6.

MEASUREMENTS

Mini-Mental State Examination (MMSE), plasma folate, vitamin B-12, methylmalonic acid, homocysteine, demographic factors, and body mass index.

RESULTS

MMSE scores declined by 0.24 points per year over the 8-year follow-up period. Decline was significantly faster in cohort members in the bottom two plasma vitamin B-12 quintile categories, and no apparent cognitive advantage was associated with plasma vitamin B-12 from 187 to 256.8 pmol/L over less than 186 pmol/L. In cohort members with plasma vitamin B-12 less than 258 pmol/L, having a plasma folate concentration greater than 20.2 nmol/L was associated with an approximate 1-point per year decline, as was use of supplemental folate.

CONCLUSION

Plasma vitamin B-12 levels from 187 to 256.8 pmol/L predict cognitive decline. Furthermore, having plasma vitamin B-12 levels in this range or below in conjunction with high plasma folate or supplemental folate use predicts especially rapid cognitive decline.

Elevated vitamin B₁₂ levels in autoimmune lymphoproliferative syndrome attributable to elevated haptocorrin in lymphocytes

OBJECTIVE

Identify the etiology of elevated B(12) in autoimmune lymphoproliferative syndrome (ALPS).

DESIGN

Peripheral blood of ALPS patients with elevated B(12) and controls were evaluated.

RESULTS

Total and holo-haptocorrin (HC) levels were 26- and 23-fold higher in ALPS patients, respectively. No abnormal B(12)-binding proteins were found. Western blot revealed HC in lymphocyte lysates only from ALPS patients.

CONCLUSION

Elevated concentrations of B(12) found in ALPS patients were due to increased lymphocyte expression of HC.

Cobalamin deficiency

Cobalamin (Cbl, vitamin B12) consists of a corrinoid structure with cobalt in the centre of the molecule. Neither humans nor animals are able to synthesize this vitamin. Foods of animal source are the only natural source of cobalamin in human diet. There are only two enzymatic reactions in mammalian cells that require cobalamin as cofactor. Methylcobolamin is a cofactor for methionine synthase. The enzyme methylmalonyl-CoA-mutase requires adenosylcobalamin as a cofactor. Therefore, serum concentrations of homocysteine (tHcy) and methylmalonic acid (MMA) will increase in cobalamin deficiency. The cobalamin absorption from diet is a complex process that involves different proteins: haptocorrin, intrinsic factor and transcobalamin (TC). Cobalamin that is bound to TC is called holotranscobalamin (holoTC) which is the metabolically active vitamin B12 fraction. HoloTC consists 6 and 20% of total cobalamin whereas 80% of total serum cobalamin is bound to another binding protein, haptocorrin. Cobalamin deficiency is common worldwide. Cobalamin malabsorption is common in elderly subjects which might explain low vitamin status. Subjects who ingest low amount of cobalamin like vegetarians develop vitamin deficiency. No single parameter can be used to diagnose cobalamin deficiency. Total serum cobalamin is neither sensitive nor it is specific for cobalamin deficiency. This might explain why many deficient subjects would be overlooked by utilizing total cobalamin as status marker. Concentration of holotranscobalamin (holoTC) in serum is an earlier marker that becomes decreased before total serum cobalamin. Concentrations of MMA and tHcy increase in blood of cobalamin deficient subjects. Despite limitations of these markers in patients with renal dysfunction, concentrations of MMA and tHcy are useful functional markers of cobalamin status. The combined use of holoTC and MMA assays may better indicate cobalamin status than either of them. Because Cbl deficiency is a risk factor for neurodegenerative diseases an early diagnosis of a low B12 status is required which should be followed by an effective treatment in order to prevent irreversible damages.

Mortality predictors in hospitalized elderly patients

AIM

To find out which of the two predictors, Charlson co-morbidity index or vitamin B12, better estimates the risk of in-hospital mortality in seriously ill patients.

METHOD

Electronic hospital records of 1509 elderly patients aged 65 and older were retrospectively surveyed.

RESULTS

Albumin, age and elevated vitamin B12 levels were significantly associated with increased in-hospital mortality. Charlson co-morbidity index was not significantly associated with death. The highest mortality (24.3%) was found in the group of patients who were concomitantly in the lowest albumin quartile and the highest vitamin B12 levels quartile. In this group, mortality increased significantly with age. By elasticity calculation, vitamin B12 capability to predict mortality was higher by ≈ 3 times than that of Charlson co-morbidity index.

CONCLUSION

In view of the fact that vitamin B12 levels have been found to predict mortality, they should be measured in geriatric practice, in addition to albumin levels, as a practical and reliable tool for identifying high risk elderly hospitalized patients. Probably, a combination of two or more available and inexpensive routinely taken tests can give a better estimation of mortality than some complicated tools, like Charlson co-morbidity index.

Advanced glycation end products overload might explain intracellular cobalamin deficiency in renal dysfunction, diabetes and aging

Advanced glycation end products (AGEs) contribute to aging. Cobalamin (Cbl) is required for cell growth and functions, and its deficiency causes serious complications. Diabetics and renal patients show high concentrations of Cbl, but metabolic evidence of Cbl deficiency that is reversible after Cbl treatment. Cbl might be sequestered in blood and cannot be delivered to the cell. Megalin mediates the uptake of transcobalamin-Cbl complex into the proximal tubule cells. Megalin is involved in the uptake and degradation of AGEs. In aging, diabetes or renal dysfunction, AGEs might overload megalin thus lowering Cbl uptake. Transcobalamin-Cbl might retain in blood. Shedding of megalin and transcobalamin receptor under glycation conditions is also a possible mechanism of this phenomenon.

Holotranscobalamin, a marker of vitamin B-12 status: analytical aspects and clinical utility

Approximately one-quarter of circulating cobalamin (vitamin B-12) binds to transcobalamin (holoTC) and is thereby available for the cells of the body. For this reason, holoTC is also referred to as active vitamin B-12. HoloTC was suggested as an optimal marker of early vitamin B-12 deficiency >20 y ago. This suggestion led to the development of suitable assays for measurement of the compound and clinical studies that aimed to show the benefit of measurement of holoTC rather than of vitamin B-12. Today holoTC can be analyzed by 3 methods: direct measurement of the complex between transcobalamin and vitamin B-12, measurement of vitamin B-12 attached to transcobalamin, or measurement of the amount of transcobalamin saturated with vitamin B-12. These 3 methods give similar results, but direct measurement of holoTC complex is preferable in the clinical setting from a practical point of view. HoloTC measurement has proven useful for the identification of the few patients who suffer from transcobalamin deficiency. In addition, holoTC is part of the CobaSorb test and therefore useful for assessment of vitamin B-12 absorption. Clinical studies that compare the ability of holoTC and vitamin B-12 to identify individuals with vitamin B-12 deficiency (elevated concentration of methylmalonic acid) suggest that holoTC performs better than total vitamin B-12. To date, holoTC has not been used for population-based assessments of vitamin B-12 status, but we suggest that holoTC is a better marker than total vitamin B-12 for such studies.

Biomarkers of cobalamin (vitamin B-12) status in the epidemiologic setting: a critical overview of context, applications, and performance characteristics of cobalamin, methylmalonic acid, and holotranscobalamin II

Cobalamin deficiency is relatively common, but the great majority of cases in epidemiologic surveys have subclinical cobalamin deficiency (SCCD), not classical clinical deficiency. Because SCCD has no known clinical expression, its diagnosis depends solely on biochemical biomarkers, whose optimal application becomes crucial yet remains unsettled. This review critically examines the current diagnostic concepts, tools, and interpretations. Their exploration begins with understanding that SCCD differs from clinical deficiency not just in degree of deficiency but in fundamental pathophysiology, causes, likelihood and rate of progression, and known health risks (the causation of which by SCCD awaits proof by randomized clinical trials). Conclusions from SCCD data, therefore, often may not apply to clinical deficiency and vice versa. Although many investigators view cobalamin testing as unreliable, cobalamin, like all diagnostic biomarkers, performs satisfactorily in clinical deficiency but less well in SCCD. The lack of a diagnostic gold standard limits the ability to weigh the performance characteristics of metabolic biomarkers such as methylmalonic acid (MMA) and holotranscobalamin II, whose specificities remain incompletely defined outside their relations to each other. Variable cutoff selections affect diagnostic conclusions heavily and need to be much better rationalized. The maximization of reliability and specificity of diagnosis is far more important today than the identification of ever-earlier stages of SCCD. The limitations of all current biomarkers make the combination of ≥2 test result abnormalities, such as cobalamin and MMA, the most reliable approach to diagnosing deficiency in the research setting; reliance on one test alone courts frequent misdiagnosis. Much work remains to be done.

Neurologic presentations of nutritional deficiencies

Optimal functioning of the central and peripheral nervous system is dependent on a constant supply of appropriate nutrients. The first section of this review discusses neurologic manifestations related to deficiency of key nutrients such as vitamin B(12), folate, copper, vitamin E, thiamine, and others. The second section addresses neurologic complications related to bariatric surgery. The third sections includes neurologic presentations caused by nutrient deficiencies in the setting of alcoholism. The concluding section addresses neurologic deficiency diseases that have a geographic predilection.

Serum cobalamin concentrations in healthy cats and cats with non-alimentary tract illness in Australia

OBJECTIVE

To determine a reference range for serum cobalamin concentration in healthy cats in Australia using a chemiluminescent enzyme immunoassay and to prospectively investigate the prevalence of hypocobalaminaemia in cats with non-alimentary tract disease.

DESIGN

Prospective study measuring serum cobalamin concentrations in clinically healthy cats and cats with non-alimentary tract illness.

PROCEDURE

Blood was collected from 50 clinically healthy cats that were owned by staff and associates of Veterinary Specialist Services or were owned animals presented to Creek Road Cat Clinic for routine vaccination. Blood was collected from 47 cats with non-alimentary tract illness presented at either clinic. Serum cobalamin concentration was determined for each group using a chemiluminescent enzyme immunoassay.

RESULTS

A reference range for Australian cats calculated using the central 95th percentile in the 50 clinically healthy cats was 345 to 3668 pg/mL. Median serum cobalamin concentration in 47 cats with non-alimentary tract illness (1186 pg/mL; range 117-3480) was not significantly different to the median serum cobalamin of the 50 healthy cats (1213 pg/mL, range 311-3688). Using the calculated reference range one sick cat with non-alimentary tract illness had a markedly low serum cobalamin concentration.

CONCLUSION

Although hypocobalaminaemia is uncommon in sick cats with non-alimentary tract illness in Australia, its occurrence in this study warrants further investigation.

An IgG complexed form of vitamin B12 is a common cause of elevated serum concentrations

OBJECTIVES

To report detailed investigations in a case of elevated serum B(12) due to the presence of an IgG-B(12) complex, to determine the prevalence of this phenomenon and to review the literature.

DESIGN AND METHODS

431 samples with elevated B(12) (median 1250 ng/L, range 901-114,480 ng/L) were treated with polyethylene glycol to precipitate immunoglobulin complexes. Samples with >50% of precipitable B(12) (PPB(12)) were further investigated by protein G adsorption, gel filtration chromatography and measurement of B(12) on different analytical platforms.

RESULTS

Median PPB(12) was 22.6%, but in 35 samples (8.1%), median PPB(12) was more than 50%. Investigation of 27 of these samples with protein G-Sepharose confirmed the presence of an IgG-B(12) complex in 24, and in 15 cases, B(12) fell to within the reference range. After treatment of serum with reagents releasing B(12) from binding proteins, immunoreactivity co-eluted with free B(12). Immunoreactivity of the IgG-bound form of B(12) was confirmed using five B(12) assays in common use in the UK.

CONCLUSIONS

At least 8% of samples with elevated vitamin B(12) contain an immunoglobulin complexed form of circulating B(12); this possibility should be considered in the interpretation of results.

Fraction of total plasma vitamin B12 bound to transcobalamin correlates with cognitive function in elderly Latinos with depressive symptoms

BACKGROUND

The fraction of total plasma vitamin B(12) bound to transcobalamin (holoTC/B12 ratio) may reflect tissue levels of the vitamin, but its clinical relevance is unclear.

METHODS

We assessed associations between cognitive function and total B12, holoTC, and holoTC/B12 ratio in a cohort of elderly Latinos (n = 1089, age 60-101 years). We assessed cognitive function using the Modified Mini-Mental State Examination (3MSE) and a delayed recall test; we diagnosed clinical cognitive impairment by neuropsychological and clinical exam with expert adjudication; and we assessed depressive symptoms using the Center for Epidemiological Studies Depression Scale (CES-D). We measured total B12 and holoTC using radioassays.

RESULTS

HoloTC/B12 ratio was directly associated with 3MSE score (P = 0.026) but not delayed recall score. Interactions between holoTC/B12 and CES-D score were observed for 3MSE (P = 0.026) and delayed recall scores (P = 0.013) such that associations between the ratio and cognitive function scores were confined to individuals with CES-D >/=16. For individuals with CES-D > or = 16, the odds ratio for clinical cognitive impairment for the lowest holoTC/B12 tertile was 3.6 (95% CI 1.2-11.2) compared with the highest tertile (P = 0.03). We observed no associations between cognitive function and total B12 or holoTC alone, except between holoTC and 3MSE score (P = 0.021), and no interactions between holoTC or total B12 and CES-D score on cognitive function.

CONCLUSIONS

HoloTC/B12 ratio is associated with cognitive function in elderly Latinos with depressive symptoms and may better reflect the adequacy of B12 for nervous system function than either holoTC or total B12 alone.