Homocysteine, Vitamin B₁₂, and Serum and Erythrocyte Folate in Peritoneal Dialysis and Hemodialysis Patients

Abstract

Background Plasma homocysteine (Hcy) is an independent risk factor for cardiovascular disease. High levels of plasma Hcy have been observed in end-stage renal disease patients. Few studies have compared peritoneal dialysis (PD) and hemodialysis (HD) patients and few data are available on erythrocyte folate (ery-F) levels in dialysis patients. Objectives To evaluate plasma Hcy concentrations, vitamin B12 (B12), and folate status in dialysis patients; to analyze the possible causes of high Hcy levels; to follow up changes in folate and B12 concentrations after 6 months. Design A cross-sectional observational study. Setting Nephrology division and laboratory of hematology in a university and clinical research hospital. Patients The study included 82 patients treated with PD for 37 ± 37 months and 70 patients treated with HD for 136 ± 95 months. Laboratory Methods Plasma Hcy was measured by the immunoenzymatic IMx Hcy FPIA method (Abbott Laboratories, Diagnostic Division, Abbott Park, IL, U.S.A.), serum folate (s-F) and ery-F by the Stratus folate fluorometric enzyme-linked assay, and B12 by the Stratus vitamin B12 fluorometric enzyme-linked assay (DADE-Behring, Newark, DE, U.S.A.). Results Ninety-six percent of PD and 97% of HD patients had Hcy levels above the cutoff (13.5 μmol/L). Homocysteine level was higher in HD than in PD patients, while the prevalence of hyperhomocysteinemia was similar with the two techniques. Erythrocyte folate was significantly higher in PD (1333 ± 519 pmol/L) than in HD (1049 ± 511 pmol/L, p < 0.01). Statistically significant correlations were observed between Hcy and B12, s-F, ery-F, and dialysis duration. Multivariate analysis showed a strong correlation between s-F and Hcy. After 6 months there were no differences in Hcy, B12, s-F, and ery-F levels. Conclusions Plasma Hcy levels were high in more than 95% of our dialysis patients, with no relation to the type of dialysis. Vitamin B12 and folate were normal in the majority of our patients. However, serum folate was the major determinant of Hcy levels. Such a relation between Hcy and folate suggests that levels of folate within the reference interval are inadequate for dialysis patients.

Guidelines for the diagnosis and treatment of cobalamin and folate disorders

“… Haemodialysis : Given that serum folate levels are reduced in the immediate post‐dialysis period, red cell folate may be the preferable assay soon after dialysis (Heinz et al , ). However, for pre‐dialysis assessment, the serum folate assay may be preferable (De Vecchi et al , ). …”

Resistance of dialyzed patients to erythropoietin

“… 62 Besides the changes in erythropoiesis, folic acid and vitamin B12 deficiencies can lead to increases in homocysteine levels, which in turn is associated with an increased risk of cardiovascular complications in renal patients. 63,64 …”

Homocysteine and Cardiovascular Risk in Dialysis Patients

“…Relatively few studies have compared Hcy levels in HD and PD. This comparison is the subject of the article by De Vecchi et al in the present issue (12). There are several reasons why Hcy levels might differ between HD and PD.…”