Assessment of thiamin status in chronic renal failure patients, transplant recipients and hemodialysis patients receiving a multivitamin supplementation

Assessment and management of vitamin status in children with CKD stages 2-5, on dialysis and post-transplantation: clinical practice points from the Pediatric Renal Nutrition Taskforce

Children with chronic kidney disease (CKD) are at risk for vitamin deficiency or excess. Vitamin status can be affected by diet, supplements, kidney function, medications, and dialysis. Little is known about vitamin requirements in CKD, leading to practice variation.The Pediatric Renal Nutrition Taskforce (PRNT), an international team of pediatric kidney dietitians and pediatric nephrologists, was established to develop evidence-based clinical practice points (CPPs) to address challenges and to serve as a resource for nutritional care. Questions were formulated using PICO (Patient, Intervention, Comparator, Outcomes), and literature searches undertaken to explore clinical practice from assessment to management of vitamin status in children with CKD stages 2-5, on dialysis and post-transplantation (CKD2-5D&T). The CPPs were developed and finalized using a Delphi consensus approach. We present six CPPs for vitamin management for children with CKD2-5D&T. We address assessment, intervention, and monitoring. We recommend avoiding supplementation of vitamin A and suggest water-soluble vitamin supplementation for those on dialysis. In the absence of evidence, a consistent structured approach to vitamin management that considers assessment and monitoring from dietary, physical, and biochemical viewpoints is needed. Careful consideration of the impact of accumulation, losses, comorbidities, and medications needs to be explored for the individual child and vitamin before supplementation can be considered. When supplementing, care needs to be taken not to over-prescribe. Research recommendations are suggested.

Vitamin Supplement Use in Patients With CKD: Worth the Pill Burden?

All vitamins play essential roles in various aspects of body function and systems. Patients with chronic kidney disease (CKD), including those receiving dialysis, may be at increased risk of developing vitamin deficiencies due to anorexia, poor dietary intake, protein energy wasting, restricted diet, dialysis loss, or inadequate sun exposure for vitamin D. However, clinical manifestations of most vitamin deficiencies are usually subtle or undetected in this population. Testing for circulating levels is not undertaken for most vitamins except folate, B12, and 25-hydroxyvitamin D because assays may not be available or may be costly to perform and do not always correlate with body stores. The last systematic review through 2016 was performed for the Kidney Disease Outcome Quality Initiative (KDOQI) 2020 Nutrition Guideline update, so this article summarizes the more recent evidence. We review the use of vitamins supplementation in the CKD population. To date there have been no randomized trials to support the benefits of any vitamin supplementation for kidney, cardiovascular, or patient-centered outcomes. The decision to supplement water-soluble vitamins should be individualized, taking account the patient's dietary intake, nutritional status, risk of vitamins deficiency/insufficiency, CKD stage, comorbid status, and dialysis loss. Nutritional vitamin D deficiency should be corrected, but the supplementation dose and formulation need to be personalized, taking into consideration the degree of 25-hydroxyvitamin D deficiency, parathyroid hormone levels, CKD stage, and local formulation. Routine supplementation of vitamins A and E is not supported due to potential toxicity. Although more trial data are required to elucidate the roles of vitamin supplementation, all patients with CKD should undergo periodic assessment of dietary intake and aim to receive various vitamins through natural food sources and a healthy eating pattern that includes vitamin-dense foods.

High-flux Hemodialysis Does Not Increase Vitamin B Loss Compared With Low-flux Hemodialysis

OBJECTIVES

A consistent effect of hemodialysis (HD) on vitamin B loss has not been fully demonstrated and the effect of high-flux hemodialysis (HFHD) is also inconclusive. The aim of this study was to identify the loss of vitamin B1, B3, B5, and B6 in a single HD session and to evaluate the effect of HFHD on vitamin B removal.

METHODS

Patients on maintenance HD were enrolled in this study. They were divided into low-flux hemodialysis (LFHD) group and HFHD group. Vitamin B1, B3, B5, and B6 (pyridoxal 5'-phosphate [PLP]) concentrations in blood pre- and post-HD sessions, as well as in the spent dialysate were measured. Loss of vitamin B was calculated and the difference in vitamin B loss between the 2 groups was compared. The association between HFHD and vitamin B loss was estimated using multivariable linear regression analysis.

RESULTS

Seventy-six patients were included, of whom 29 were on LFHD and 47 were on HFHD. The median reduction ratio of serum vitamins B1, B3, B5, and B6 after a single HD session was 38.1%, 24.9%, 48.4%, and 44.7%, respectively. The median concentration of vitamins B1, B3, B5, and B6 in the dialysate was 0.3 μg/L, 2.9 μg/mL, 2.0 μg/L, and 0.4 ng/mL. There was no difference in either the reduction ratio of vitamin B in blood, or the concentration in dialysate between LFHD and HFHD groups. After adjusting for covariates by multivariable regression, HFHD had no effect on vitamin B1, B3, B5, or B6 removal.

CONCLUSIONS

Vitamins B1, B3, B5, and B6 can be removed by HD and HFHD does not increase the loss.

Does Vitamin Supplementation Play a Role in Chronic Kidney Disease?

Although the role of vitamins in the human body is proven, guidelines for patients with chronic kidney disease (CKD) remain unclear. This narrative review summarizes the findings of 98 studies of CKD and the effects of vitamin D, B, C, A, E, and K supplementation on patients on dialysis for CKD, with the aim of summarizing the existing guidelines. The findings are promising, showing the potential effectiveness of vitamin supplementation with, for example, vitamins B, D, or C. However, recommendations are still ambiguous, especially in the case of vitamins A and K, due to the potential toxicity associated with higher doses for patients. Continued research is needed to rigorously evaluate the effectiveness and carefully consider the potential risks of some vitamin supplementation for patients with CKD.

Demand for Water-Soluble Vitamins in a Group of Patients with CKD versus Interventions and Supplementation-A Systematic Review

BACKGROUND

Increasingly, chronic kidney disease (CKD) is becoming an inevitable consequence of obesity, metabolic syndrome, and diabetes. As the disease progresses, and through dialysis, the need for and loss of water-soluble vitamins both increase. This review article looks at the benefits and possible risks of supplementing these vitamins with the treatment of CKD.

METHODS

Data in the PubMed and Embase databases were analyzed. The keywords "chronic kidney disease", in various combinations, are associated with thiamin, riboflavin, pyridoxine, pantothenic acid, folates, niacin, cobalamin, and vitamin C. This review focuses on the possible use of water-soluble vitamin supplementation to improve pharmacological responses and the overall clinical condition of patients.

RESULTS

The mechanism of supportive supplementation is based on reducing oxidative stress, covering the increased demand and losses resulting from the treatment method. In the initial period of failure (G2-G3a), it does not require intervention, but later, especially in the case of inadequate nutrition, the inclusion of supplementation with folate and cobalamin may bring benefits. Such supplementation seems to be a necessity in patients with stage G4 or G5 (uremia). Conversely, the inclusion of additional B6 supplementation to reduce CV risk may be considered. At stage 3b and beyond (stages 4-5), the inclusion of niacin at a dose of 400-1000 mg, depending on the patient's tolerance, is required to lower the phosphate level. The inclusion of supplementation with thiamine and other water-soluble vitamins, especially in peritoneal dialysis and hemodialysis patients, is necessary for reducing dialysis losses. Allowing hemodialysis patients to take low doses of oral vitamin C effectively reduces erythropoietin dose requirements and improves anemia in functional iron-deficient patients. However, it should be considered that doses of B vitamins that are several times higher than the recommended dietary allowance of consumption may exacerbate left ventricular diastolic dysfunction in CKD patients.

CONCLUSIONS

Taking into account the research conducted so far, it seems that the use of vitamin supplementation in CKD patients may have a positive impact on the treatment process and maintaining a disease-free condition.

KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for nutrition in kidney diseases since 1999. Since the publication of the first KDOQI nutrition guideline, there has been a great accumulation of new evidence regarding the management of nutritional aspects of kidney disease and sophistication in the guidelines process. The 2020 update to the KDOQI Clinical Practice Guideline for Nutrition in CKD was developed as a joint effort with the Academy of Nutrition and Dietetics (Academy). It provides comprehensive up-to-date information on the understanding and care of patients with chronic kidney disease (CKD), especially in terms of their metabolic and nutritional milieu for the practicing clinician and allied health care workers. The guideline was expanded to include not only patients with end-stage kidney disease or advanced CKD, but also patients with stages 1-5 CKD who are not receiving dialysis and patients with a functional kidney transplant. The updated guideline statements focus on 6 primary areas: nutritional assessment, medical nutrition therapy (MNT), dietary protein and energy intake, nutritional supplementation, micronutrients, and electrolytes. The guidelines primarily cover dietary management rather than all possible nutritional interventions. The evidence data and guideline statements were evaluated using Grading of Recommendations, Assessment, Development and Evaluation (GRADE) criteria. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

Prevalence of Low Plasma Vitamin B1 in the Stroke Population Admitted to Acute Inpatient Rehabilitation

OBJECTIVE

To determine the prevalence of vitamin B1 (VitB1) deficiency in the stroke population admitted to acute inpatient rehabilitation.

DESIGN

Retrospective cohort study.

SETTING

Acute inpatient rehabilitation facility at an academic medical center.

PARTICIPANTS

119 consecutive stroke patients admitted to stroke service from 1 January 2018 to 31 December 2018.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Plasma VitB1 level.

RESULTS

There were 17 patients (14%; 95% CI 9-22%) with low VitB1 with a range of 2-3 nmol/L, an additional 58 (49%; CI 40-58%) patients had normal low VitB1 with a range of 4-9 nmol/L, twenty-five patients (21%; CI 15-29%) had normal high VitB1 with a range of 10-15 nmol/L, and nineteen patients (16%; CI 10-24%) had high VitB1 with a range of 16-43 nmol/L.

CONCLUSIONS

In this cohort of patients admitted to the stroke service at an acute rehabilitation facility, there is evidence of thiamine deficiency. Moreover, the data suggest that there is inadequate acute intake of VitB1. Given the role of thiamine deficiency in neurologic function, further study of the role of thiamine optimization in the acute stroke rehabilitation population is warranted.

Thiamine Diphosphate Status and Dialysis-Related Losses in End-Stage Kidney Disease Patients Treated with Hemodialysis

Aim: (1) To describe the whole blood content of thiamine diphosphate (TDP), a biologically active form of vitamin B1 in end-stage kidney disease patients treated with hemodialysis (HD); (2) to establish the impact of a single HD procedure on TDP blood concentrations; and (3) to describe potential explanatory variables influencing TDP dialysis related losses, including dialysis prescription, vitamin B1 dietary intake and supplementation. Methods: Single-center, cross-sectional study in 50 clinically stable maintenance HD patients. The assessment of whole blood TDP with the High Performance Liquid Chromatography method, before and after a single, middle-week dialysis session and analysis of clinical and laboratory parameters potentially influencing TDP status Results: We report a significant difference in TDP levels before and after HD sessions - 42.5 (95% CI 38.7-46.2) μg/L and 23.6 (95% CI 18.9-28.2) μg/L, respectively (p = 0.000). The magnitude of intradialytic TDP changes is highly variable among individuals and is negatively associated only with the body weight of the patients (p < 0.013). Vitamin B1 dietary intake and supplementation do not influence whole blood TDP and dialysis-related loss of TDP. Conclusions: TDP, a bioactive compound of vitamin B1, is substantially lost during the HD procedure, and the magnitude of its loss is associated with the patient's body weight but it is not influenced by vitamin B1 dietary intake and standard supplementation dose.

High rate of thiamine deficiency among inpatients with cancer referred for psychiatric consultation: results of a single site prevalence study

OBJECTIVE

Thiamine deficiency (TD) is increasingly recognized in medically ill patients. The prevalence of TD among cancer patients is unknown. This study aims to characterize the prevalence of TD among inpatients with cancer.

METHODS

Retrospective chart review of patients admitted to a large cancer center who were referred for psychiatric consultation and whose serum thiamine concentration was measured. Patients with alcohol use were excluded.

RESULTS

Among 217 patients with various cancer types, TD was found in 55.3%. Risk factors included fluorouracil-based chemotherapy, significant weight loss, and undergoing active cancer treatment. Almost all patients were normal weight, overweight, or obese, and few had concomitant vitamin B12 or folate deficiency. A total of 17.5% were receiving multivitamin supplementation. Nearly half (49.8%) did not receive empiric treatment with thiamine and among those who did, treatment delay occurred in the majority of cases (59.6%). Measurement of serum thiamine concentration preceded psychiatric consultation in only 10.6% of cases.

CONCLUSIONS

Our findings suggest that TD is highly prevalent among inpatients with cancer, even among normal and overweight individuals, in the absence of other vitamin deficiencies, and while receiving multivitamin supplements. Several potential risk factors were identified, including active cancer treatment. Evaluation of TD was most commonly not initiated by oncologists. Failure to treat and treatment delay were common. Given these findings, oncologists must be vigilant about detecting TD among inpatients with cancer. Copyright © 2016 John Wiley & Sons, Ltd.

Thiamin in Clinical Practice

Thiamin is a water-soluble vitamin also known as vitamin B1. Its biologically active form, thiamin pyrophosphate (TPP), is a cofactor in macronutrient metabolism. In addition to its coenzyme roles, TPP plays a role in nerve structure and function as well as brain metabolism. Signs and symptoms of thiamin deficiency (TD) include lactic acidosis, peripheral neuropathy, ataxia, and ocular changes (eg, nystagmus). More advanced symptoms include confabulation and memory loss and/or psychosis, resulting in Wernicke's encephalopathy and/or Wernicke's Korsakoff syndrome, respectively. The nutrition support clinician should be aware of patients who may be at risk for TD. Risk factors include those patients with malnutrition due to 1 or more nutrition-related etiologies: decreased nutrient intake, increased nutrient losses, or impaired nutrient absorption. Clinical scenarios such as unexplained heart failure or lactic acidosis, renal failure with dialysis, alcoholism, starvation, hyperemesis gravidarum, or bariatric surgery may increase the risk for TD. Patients who are critically ill and require nutrition support may also be at risk for TD, especially those who are given intravenous dextrose void of thiamin repletion. Furthermore, understanding thiamin's role as a potential therapeutic agent for diabetes, some inborn errors of metabolism, and neurodegenerative diseases warrants further research. This tutorial describes the absorption, digestion, and metabolism of thiamin. Issues pertaining to thiamin in clinical practice will be described, and evidence-based practice suggestions for the prevention and treatment of TD will be discussed.

Shoshin beriberi induced by long-term administration of diuretics: a case report

Previous studies have suggested that diuretic therapy for heart failure may lead to thiamine deficiency due to the increased urinary thiamine excretion. Herein, we present the case of a 61-year-old man with shoshin beriberi, a fulminant form of wet beriberi, induced by long-term diuretic therapy. The patient had a history of heart failure with preserved ejection fraction and was receiving furosemide and trichlormethiazide therapy. He presented with worsening exertional dyspnea and was admitted for heart failure exacerbation. His condition failed to improve even after intensive treatment. A hemodynamic evaluation with the Swan-Ganz catheter revealed high-output heart failure with low peripheral vascular resistance. Thiamine was administered for suspected shoshin beriberi; his hemodynamic status improved dramatically within the next six hours. The serum thiamine level was below the normal range; the patient was therefore diagnosed with shoshin beriberi. The common causes of thiamine deficiency were not identified. Long-term diuretic therapy with furosemide and thiazide was thought to have played a major role in the development of thiamine deficiency. This case illustrates the importance of considering wet beriberi as a possible cause of heart failure exacerbation in patients taking diuretics, even when the common thiamine deficiency causes are not identified with history-taking.

Water-soluble vitamins in people with low glomerular filtration rate or on dialysis: a review

People with low glomerular filtration rate and people on dialysis are spontaneously at risk for vitamin deficiency because of the potential for problems with decreased appetite and decreased sense of smell and taste, leading to decreased intake, and because decreased energy or decreased cognitive ability results in difficulties in shopping and cooking. Imposed dietary restrictions because of their renal dysfunction and because of comorbidities such as hypertension and diabetes exacerbate this problem. Finally, particularly for water-soluble vitamins, loss may occur into the dialysate. We did not identify any randomized trials of administering daily doses close to the recommended daily allowances of these vitamins. In people who are eating at all, deficiencies of B5 and B7 seem unlikely. It is unclear whether supplements of B2 and B3 are necessary. Because of dialyzability and documented evidence of insufficiency in dialysis patients, B1 supplementation is likely to be helpful. B6, B9, and B12 are implicated in the hyperhomocysteinemia observed in patients on dialysis. These vitamins have been studied in combinations, in high doses, with the hope of reducing cardiovascular outcomes. No reductions in patient-important outcomes were seen in adequately powered randomized trials. Because of their involvement in the homocysteine pathway, however, supplementation with lower doses, close to the recommended daily allowances, may be helpful. Vitamin C deficiency is common in patients on dialysis who are not taking supplements: low-dose supplements are warranted. Vitamins for dialysis patients contain most or all of the B vitamins and low-dose vitamin C. We are not aware of any medical reasons to choose one over another.

Thiamine is a substrate of organic cation transporters in Caco-2 cells

The aim of this study was to characterize the intestinal absorption of thiamine, by investigating the hypothesis of an involvement of Organic Cation Transporter (OCT) family members in this process. [(3)H]-T(+) uptake was found to be: 1) time-dependent, 2) Na(+)- and Cl(-)-dependent, 3) pH-dependent, with uptake increasing with a decrease in extracellular pH and decreasing with a decrease in intracellular pH, 4) inhibited by amiloride, 5) inhibited by the thiamine structural analogues oxythiamine and amprolium, 6) inhibited by the unrelated organic cations MPP(+), clonidine, dopamine, serotonin, 7) inhibited by the OCT inhibitors decynium22 and progesterone. Moreover, the dependence of [(3)H]-T(+) uptake on phosphorylation/dephosphorylation mechanisms was also investigated and [(3)H]-T(+) uptake was found to be reduced by PKA activation and protein tyrosine phosphatase and alkaline phosphatase inhibition. In conclusion, our results are compatible with the possibility of thiamine being transported not only by ThTr1 and/or ThTr2, but also by members of the OCT family of transporters (most probably OCT1 and/or OCT3), thus sharing the same transporters with several other organic cations at the small intestinal level.

Thiamine supplementation in the critically ill

PURPOSE OF REVIEW

To summarize the properties of thiamine and evaluate current evidence on thiamine status and supplementation, for different populations of critically ill patients.

RECENT FINDINGS

Thiamine, in the form of thiamine pyrophosphate, is a critical co-factor in the glyocolysis and oxidative decarboxylation of carbohydrates for energy production. Different studies have shown that critical illness in adults and children is characterized by absolute or relative thiamine depletion, which is associated with an almost 50% increase in mortality. Thiamine deficiency should be suspected in different clinical scenarios such as severe sepsis, burns, unexplained heart failure or lactic acidosis, neurological disorder in patients with previous history of alcoholism, starvation, chronic malnutrition, long-term parenteral feeding, hyperemesis gravidarum, or bariatric surgery. Nonetheless, thiamine supplements are not routinely given to critically ill patients. Clinicians should be able to suspect and recognize risk factors for the occurrence of severe neurological disorders secondary to thiamine deficiency, as early treatment can prevent the appearance of permanent neurological damage.

SUMMARY

Symptoms and signs associated with thiamine deficiency lack sensitivity and specificity in critically ill patients. Consequently, depletion is frequently unrecognized and underdiagnosed by clinicians. Potentially deleterious consequences of thiamine depletion should be avoided by early and appropriate supplementation.

Vitamin status and needs for people with stages 3-5 chronic kidney disease

Patients with chronic kidney disease (CKD) often experience a decline in their nutrient intake starting at early stages of CKD. This reduction in intake can affect both energy-producing nutrients, such as carbohydrates, proteins, and fats, as well as vitamins, minerals, and trace elements. Knowledge of the burden and bioactivity of vitamins and their effect on the health of the patients with CKD is very incomplete. However, without sufficient data, the use of nutritional supplements to prevent inadequate intake may result in either excessive or insufficient intake of micronutrients for people with CKD. The purpose of this article is to briefly summarize the current knowledge regarding vitamin requirements for people with stages 3, 4, or 5 CKD who are not receiving dialysis.

Dietary intakes and biochemical status of B vitamins in a group of children receiving dialysis

OBJECTIVE

We investigated the dietary intake and biochemical status of B vitamins (thiamin, riboflavin, vitamin B6, and vitamin B12) in a group of mainly unsupplemented children with endstage renal disease receiving dialysis, to determine if B vitamin supplementation is indicated.

DESIGN

This was a cross-sectional, observational clinical trial.

SETTING

Children with endstage renal disease were receiving dialysis, under the care of Renal Services, at Starship Children's Health (Grafton, Auckland, New Zealand).

PATIENTS

We studied 12 children (including 7 girls, and 8 children receiving peritoneal dialysis) mean age 7.8 +/- 5.3 years (SD).

INTERVENTION

Three-day diet records were collected and analyzed with FoodWorks software. Blood was collected for vitamin assay testing.

MAIN OUTCOME MEASURE

Dietary intake of B vitamins was measured as a percentage of recommended dietary intake (RDI) or adequate intakes (AIs) for age. Biochemical status was measured as the concentration of each B vitamin compared with reference ranges.

RESULTS

Mean intakes from diet alone comprised <100% of the RDI or AI for each B vitamin. Mean intakes, with nutritional support, reached >100% of the RDI or AI for each B vitamin. All children achieved >100% RDI or AI for thiamin, riboflavin, and vitamin B12. Two children who were not receiving nutritional support received <100% of the RDI for vitamin B6. Blood levels of B vitamins were normal to high, compared with reference ranges, for each B vitamin in all children, indicating adequate status.

CONCLUSIONS

Intakes were adequate in the majority of children. Status was adequate in all children. In this group of children undergoing dialysis, B-vitamin supplementation was not indicated.

Copper, selenium, zinc, and thiamine balances during continuous venovenous hemodiafiltration in critically ill patients

BACKGROUND

Acute renal failure is a serious complication in critically ill patients and frequently requires renal replacement therapy, which alters trace element and vitamin metabolism.

OBJECTIVE

The objective was to study trace element balances during continuous renal replacement therapy (CRRT) in intensive care patients.

DESIGN

In a prospective randomized crossover trial, patients with acute renal failure received CRRT with either sodium bicarbonate (Bic) or sodium lactate (Lac) as a buffering agent over 2 consecutive 24-h periods. Copper, selenium, zinc, and thiamine were measured with highly sensitive analytic methods in plasma, replacement solutions, and effluent during 8-h periods. Balances were calculated as the difference between fluids administered and effluent losses and were compared with the recommended intakes (RI) from parenteral nutrition.

RESULTS

Nineteen sessions were conducted in 11 patients aged 65 +/- 10 y. Baseline plasma concentrations of copper were normal, whereas those of selenium and zinc were below reference ranges; glutathione peroxidase was in the lower range of normal. The replacement solutions contained no detectable copper, 0.01 micromol Se/L (Bic and Lac), and 1.42 (Bic) and 0.85 (Lac) micromol Zn/L. Micronutrients were detectable in all effluents, and losses were stable in each patient; no significant differences were found between the Bic and Lac groups. The 24-h balances were negative for selenium (-0.97 micromol, or 2 times the daily RI), copper (-6.54 micromol, or 0.3 times the daily RI), and thiamine (-4.12 mg, or 1.5 times the RI) and modestly positive for zinc (20.7 micromol, or 0.2 times the RI).

CONCLUSIONS

CRRT results in significant losses and negative balances of selenium, copper, and thiamine, which contribute to low plasma concentrations. Prolonged CRRT is likely to result in selenium and thiamine depletion despite supplementation at recommended amounts.

Riboflavin is a determinant of total homocysteine plasma concentrations in end-stage renal disease patients

The effect of thiamine (vitamin B(1)) or riboflavin (vitamin B(2)) availability on fasting total homocysteine (tHcy) plasma levels in end-stage renal disease patients is unknown. A cross-sectional study was performed in a population of non-vitamin supplemented patients maintained on continuous ambulatory peritoneal dialysis. Red blood cell availability of thiamine (alpha-ETK) and of riboflavin (alpha-EGR), along with other predictors of tHcy plasma levels, was considered in the analysis. There was a linear association of alpha-EGR with tHcy plasma concentrations (P = 0.009), which was not observed for alpha-ETK. Among red blood cell vitamins, alpha-EGR was the only predictor of tHcy levels (P = 0.035), whereas alpha-ETK, red blood cell pyridoxal-5-phosphate supply (alpha-EGOT) and red blood cell folate levels had no effect. The risk for having a high tHcy plasma levels within the fourth quartile (plasma tHcy >38.3 micromol/L) was increased by an alpha-EGR > median (odds ratio, 4.706; 95% confidence interval, 1.124 to 19.704; P = 0.026). By way of contrast, alpha-ETK had no effect in these analyses. Independent predictors of tHcy plasma levels were serum albumin, alpha-EGR, red blood cell folate, and certain MTHFR genotypes. A logistic regression analysis showed that the MTHFR genotype is a predictor for having a tHcy plasma concentration within the fourth quartile. In summary, riboflavin availability, as measured by alpha-EGR, is a determinant of fasting tHcy plasma levels in peritoneal dialysis patients. This finding may have implications for tHcy lowering therapy in individuals with end-stage renal disease.