Impedance ratio: a novel marker and a powerful predictor of mortality in hemodialysis patients.
OBJECTIVE
Impedance ratio (Imp-R) obtained by multifrequency bioimpedance analysis (BIA) has been shown to be associated with volume and nutrition status. In this prospective study, the predictive role of Imp-R for mortality in hemodialysis (HD) patients was investigated.


METHODS
Multifrequency (5-50-100-200 kHz) BIA was applied to 493 prevalent HD patients in March-April 2006. Imp-R was defined as the ratio of 200-5 kHz impedance values. Demographical, clinical and laboratory data at the time of the analysis were recorded. All-cause and cardiovascular (CV) mortality were assessed during 3 years of follow-up.


RESULTS
Mean age was 57.7 ± 13.9 years, HD duration 52.1 ± 42.6 months and prevalence of diabetes 21.7 %. Imp-R was negatively correlated with nutritional markers including albumin, creatinine and hemoglobin levels. In addition, there was a positive correlation between Imp-R and age, ratio of extracellular water to total body water and high-sensitive C-reactive protein. Over a mean follow-up period of 27.9 ± 11.1 months, 93 deaths (52 from CV reasons) were observed. In the multivariate analysis, Imp-R was significantly associated with all-cause and CV mortality after adjustments [HR 1.13, 95 % CI (1.04-1.23); p = 0.004 and HR 1.15, 95 % CI (1.03-1.27); p = 0.01, respectively]. The risk of all-cause mortality was 3.4 times higher in the fourth quartile of Imp-R (>83.5 %) compared to the first Imp-R quartile (<78.8 %) as reference. Cutoff value of Imp-R for all-cause mortality was 82.0 % with a sensitivity of 65.5 % and specificity of 64 %.


CONCLUSIONS
Impedance ratio measured by multifrequency in standardized conditions BIA is an independent and powerful predictor of both all-cause and CV mortality in hemodialysis patients.
FMC Turkey Clinics, Izmir, Turkey. demircen@hotmail.com.
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Demirci
Division of Nephrology, Ege University School of Medicine, Izmir, Turkey.
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Aşcı
Division of Nephrology, Ege University School of Medicine, Izmir, Turkey.
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Demirci
Division of Nephrology, Ege University School of Medicine, Izmir, Turkey.
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M
Özkahya
Division of Nephrology, Ege University School of Medicine, Izmir, Turkey.
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Töz
Division of Nephrology, Ege University School of Medicine, Izmir, Turkey.
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Duman
Sakarya University Training and Research Hospital, Sakarya, Turkey.
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Sipahi
FMC Turkey Clinics, Izmir, Turkey.
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Erten
Tepecik Training and Research Hospital, Izmir, Turkey.
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M
Tanrısev
Division of Nephrology, Ege University School of Medicine, Izmir, Turkey.
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Ok
D000328:Adult; D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D002423:Cause of Death; D015331:Cohort Studies; D017097:Electric Impedance; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D007676:Kidney Failure, Chronic / Q000175:diagnosis / Q000401:mortality* / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D006435:Renal Dialysis / Q000379:methods / Q000401:mortality*; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012737:Sex Factors; D016019:Survival Analysis
Bioimpedance; Hemodialysis; Impedance ratio; Inflammation; Mortality; Nutrition