Authors:
M. Kalovoulos, A. Papagianni, D. Kirmizis, D. Daravingas, A. Vainas, A.-M. Belechri, E. Alexopoulos, D. Memmos; Thessaloniki/GR
DOI:
10.1594/ECR03/C-1052
Methods and Materials
SubjectsBetween January and April 2001, 112 adult patients on chronic maintenance HD (60 male, mean age 59 years, range 2586 years) from the dialysis unit of the University Department of Nephrology at Hippokration General Hospital and from one affiliated outpatient dialysis center consecutively entered the study. All patients had been stabilized on renal replacement therapy for > 3 months (mean HD duration 74 months, range 5372 months) and were clinically stable and free of active infection. Chronic renal failure was attributed to glomerulonephritis in 46 cases, tubulointerstitial nephritis in 35, polycystic kidney disease in 11, renovascular hypertension in 4 and was undetermined in 16 cases. Patients with diabetes mellitus, liver disease, autoimmune diseases or malignancies were excluded in order to avoid the possible effects of these co-morbid conditions on cytokine production. None of the patients was receiving antibiotics, corticosteroids or cytotoxic drugs at the time of the study. Dialysis prescription was guided by a goal of achieving a value of >= 0.65 for the urea reduction ratio and a value of Kt/V >= 1.2. The above indices of adequacy of dialysis were calculated by the formula [(pre-dialysis urea)-(post-dialysisurea)/pre-dialysis urea] and by the second-generation Daugirdas equation, respectively. Seventy-five patients (67%) were receiving one or more antihypertensive drugs at the time of the study. Thirty-nine patients (34.8%) had clinical signs or a previous history of CVD. The control group consisted of 50 age-and sex-matched apparently healthy subjects (27 male, mean age 56 years, range 2585 years). These control subjects did not have any history of hypertension, diabetes mellitus and renal or vascular disease and were receiving no drugs at the time of the study. Informed consent was obtained from each patient and control subject.Laboratory methods Blood samples from HD patients and control subjects were taken from a peripheral vein under fasting conditions. Samples from HD patients were collected in the morning of a mid-week routine dialysis day. Serum levels of the circulating adhesion molecules ICAM-1, VCAM-1 and E-selectin were measured by an enzyme-linked immunosorbent assay (ELISA) using commercially available standard kits (Quantikine human sICAM-1, sVCAM-1 and sE-selectin; Research & Diagnostic Systems Europe Ltd, Abington, UK). Serum albumin, total cholesterol, triglycerides and HDL cholesterol were determined by routine techniques using an automated analyser. LDL cholesterol was calculated using the Friedewald formula. Serum CRP levels were measured by nephelometry. The detection limit was 3.75 mg/l and in the statistical evaluation all values <3.75 mg/l were treated as 3 mg/l. Carotid ultrasonography Ultrasonographic studies were performed with an Aloka Sonos SSD-1700 (Aloka, Tokyo, Japan) instrument using a 7.5 MHz high-resolution probe. The carotid artery was investigated bilaterally by the same expert radiologist (M. K.) who was unware of clinical and laboratory data. Intimamedia thickness (IMT) was defined as a low-level echo grey band that does not project into the arterial lumen and was measured at the diastolic phase as the distance between the leading edge of the first and second echogenic line. IMT was measured on the longitudinal views of the far wall of the distal segment of the common carotid artery, the carotid bifurcation and the initial tract of the internal carotid artery on both sides. Measurements were performed 0.5, 1 and 2 cm below and above the bifurcation (six measurements on each side) in a plaque-free arterial segment. The average measurement of the obtained values was taken as IMT and it was considered abnormal when it exceeded 0.82 mm [4]. Carotid plaques were defined (and counted) either as faint grey echoes (soft plaques) or bright white echoes (calcified plaques) protruding into the arterial lumen. Plaque thickness was measured in a suitable longitudinal or transverse view. Plaque score was computed by summing maximum thickness in millimeters of plaques in each segment on both sides.Statistical analysisData are expressed as meanSD and with range. The significance of differences in mean between the two groups was assessed by Students t-test or MannWhitney test as appropriate. Differences in proportions were tested with the use of x2 statistic. Correlations were tested by regression analysis. Non-normally distributed variables were log-transformed before entering regression analysis. Multiple regression analysis with a forward elimination procedure was used to assess the combined influence of variables on IMT and plaque score values. The following variables were used: age, sex, smoking, HD duration, history of CVD, systolic and diastolic blood pressure (BP), serum cholesterol, triglycerides, HDL, LDL, logCRP, ICAM-1, VCAM-1 and E-selectin levels. A two-tailed P value < 0.05 was considered statistically significant.