Do dialysis patients need extra folate supplementation?

To assess folate status and to evaluate the need for conventional folate supplementation in patients on dialysis, we measured serum folate, vitamin B12, and red cell folate concentrations by radioimmunoassay. Thirty-four continuous ambulatory peritoneal dialysis (CAPD) patients and 60 hemodialysis (HD) patients who had not been supplemented with folate were enrolled. Serum folate levels (5.8 +/- 3.6 ng/mL vs 2.0 +/- 1.1 ng/mL, p < 0.001) and vitamin B12 levels (831.4 +/- 416.9 pg/mL vs 513.9 +/- 213.3 pg/mL, p < 0.001) were significantly higher in CAPD patients than HD patients. The red cell folate levels (849.7 +/- 489.4 ng/mL vs 491.0 +/- 253.2 ng/mL, p < 0.001) were also significantly higher in CAPD patients. The incidences of folate deficiency in CAPD and HD patients were overestimated using the cut-off value for serum folate concentration (3.0% vs 71.7%, respectively), but the incidence of true folate deficiency was lower using the cut-off value for red cell folate level (0.0% vs 10.0%, respectively). In conclusion, the true incidence of folate deficiency in stable CAPD and HD patients is surprisingly low, even in patients who may not be taking folate supplements. The need for conventional folate supplementation in patients with end-stage renal disease on dialysis must therefore be re-evaluated. Before the decision is made to use folate supplementation, measurement of red cell folate is essential to assess of folate reserves of the patients on dialysis.