Amedeo F. De Vecchi

Free and total plasma malondialdehyde in chronic renal insufficiency and in dialysis patients

BACKGROUND Available data about oxidative status in patients with end-stage renal disease (ESRD) or on dialysis are contradictory. The present cross-sectional study aimed to investigate the role of renal insufficiency and dialysis on lipid peroxidation. To separate the effects of uraemia from dialysis-induced stress, we enrolled 26 patients with renal insufficiency on conservative treatment (ESRD), 23 on peritoneal dialysis (PD), 30 on haemodialysis (HD) and 30 controls. METHODS Plasma malondialdehyde (MDA) levels, both total (tMDA) and free (fMDA), were measured as indexes of oxidative stress by gas chromatography-mass spectrometry. Bound MDA (bMDA) levels were calculated as the difference between tMDA and fMDA. RESULTS Total and bMDA concentrations were significantly higher in patients than in controls (ESRD > HD > PD). In PD and HD patients, fMDA levels were similar and significantly higher than in ESRD. Multivariate analysis, with tMDA, fMDA and bMDA as dependent variables, showed similar and significant tMDA and bMDA relations with residual renal function (t = -2.160, P = 0.035) and albumin (t = -2.049, P = 0.045). Erythropoietin dose affected only fMDA values (t = -2.178, P = 0.034). CONCLUSIONS Free and bMDA concentrations identified different MDA patterns. Bound MDA, not excreted by kidneys, accounts alone for high tMDA concentrations in ESRD patients, while both fMDA and bMDA contribute to tMDA values in dialysis patients. These findings show that increased tMDA could be indicative not only of recent lipid peroxidation, and they also highlight the importance of evaluating free, bound and total MDA in patients with reduced renal function in order to assess their oxidative status.

Folate Supplementation in Peritoneal Dialysis Patients with Normal Erythrocyte Folate: Effect on Plasma Homocysteine

The possible role of folate supplementation in reducing hyperhomocysteinemia in dialysis patients has been reported in several recent papers. However, scant data are available for peritoneal dialysis patients; besides, none of these studies investigated either the role of intraerythrocyte folate concentration or the presence of side effects caused by folate administration. Sixty-six peritoneal dialysis patients with hyperhomocysteinemia (>15 µmol/l) and normal folate status (as assessed by erythrocyte folate level >600 nmol/l) were randomly allocated to receive either oral folate (5 mg/day) or no vitamin supplementation. After 2 months of therapy, patients were requested to answer a questionnaire investigating the occurrence of symptoms possibly related to folate supplementation. Twenty-nine treated patients and 30 untreated controls completed the study. In the treated patients, serum and erythrocyte folate increased significantly (p < 0.0001) (respectively from 10.6 ± 4.9 to 237 ± 231 nmol/l and from 1,201 ± 297 to 2,881 ± 294 nmol/l) to levels at the uppermost limit of detection by laboratory methods. Serum vitamin B12 levels did not change. Plasma homocysteine levels decreased from 54 ± 32 to 23 ± 14 µmol/l after folate supplementation and remained unchanged in the control group. After 4 months of folate therapy, homocysteine concentration was within the normal range in 5 patients (17%) and below 30 µmol/l in the other 21 (72%). Folate therapy resulted in a decrease in homocysteine of more than 50% in 45% of the patients and decrease of more than 20% in a further 38%. No significant symptoms were reported. Thus, serum and erythrocyte folate increase confirms that normal folate levels are inadequate in dialysis patients, even if serum and erythrocyte levels before folate supplementation cannot predict the effect on homocysteine plasma levels.

Erythrocyte ferritin concentration: Analytical performance of the immunoenzymatic IMx-Ferritin (Abbott) assay

Abstract Together with serum ferritin, erythrocyte ferritincan be a valuable diagnostic tool for evaluating the degree of impaired iron metabolism in different diseases. We collected peripheral blood samples from 64 subjects (22 healthy volunteers, 20 patients with hereditary hemochromatosis, and 22 patients on regular hemodialysis with secondary anemia) to evaluate whether an immunoenzymatic method generally used for serum ferritin can also be used to determine erythrocyte ferritin levels under various conditions of body iron status. Serum and erythrocyte ferritin levels were assayed in parallel using a microparticle enzyme immunoassay (MEIA) IMx-Ferritin kit and an IMx analyzer. The inter-assay imprecision of the serum and erythrocyte ferritin assays was 4.9% and 5.05%, the intra-assay imprecision was 2.2% and 2.3%, and the mean recovery was 102% (range 96–105%) and 101% (range 99–105%), respectively. Both serum and erythrocyte ferritin assays showed a detection limit of 1μg/L and good linearity (R 2=0.99) in the intervals 13.9–443 and 3.9–135.6μg/L, respectively. Our findings demonstrate that the IMx-Ferritin assay currently used to measure serum ferritin levels can also be adopted to measure erythrocyte ferritin insofar as it clearly discriminates high and low erythrocyte ferritin levels in cases of both iron overload and deficiency.

Nine patients treated for more than 10 years with continuous ambulatory peritoneal dialysis

We have retrospectively examined the clinical outcomes of the 9 patients who survived for more than 10 years in our continuous ambulatory peritoneal dialysis (CAPD) program. Six were men and 3 women aged 50.8 +/- (SD) 11.5 years. Three had been previously treated by hemodialysis. None of them had diabetes or neoplasms, 1 had liver cirrhosis, 3 had ischemic cardiopathy, 1 had peripheral artery disease, and all were hypertensive. The hospitalization rate ranged from 0 to 4.5 days/patient/year, the peritonitis rate was one episode every 57 months. Six patients had no peritonitis during the first 10 years of treatment. Exit-site episodes were one every 46.7 patient months. Six peritoneal catheters were removed from 4 patients. KT/V and peritoneal permeability, assessed by the peritoneal equilibration test, were within the normal range in the majority of the patients. Five patients died between the 121st and the 149th month, and 4 are still alive. Three of them are working. These results show that CAPD can be effective, peritoneal catheters can survive, and some patients can be free from peritonitis episodes for more than 10 years. After the 10-year on CAPD, the survival is poor, and the morbidity is high.