Effect of body composition on dialysis quality(Kt/V): a single center study

Objective To investigate the relationship between body composition and adequacy of dialysis, and analyze the related risk factors for inadequate delivery of hemodialysis. Methods In a prospective clinical trial, two different methods determining dialysis dose were simultaneously applied: Kt/Vdau (conventional method with Daugirdas' formula) and Kt/Vbcm [online clearance monitoring (OCM) measurement with V measured by body composition monitor (BCM)]. Using the value of 1.27 as the boundary, the patients were divided into two groups: Kt/Vbcm<1.27 group and Kt/Vbcm≥1.27 group. Clinical indices were compared between the two groups. Multiple linear regression was applied to analyze the potential impact factors of the difference between Kt/V values calculated by the two methods. Receiver operator characteristic (ROC) curve was applied to analyze meaningful factors. Results A total of 138 maintenance hemodialysis patients with age of (54.9±12.7) years old were enrolled, and 55.1% of them were males. There was no significant difference between Kt/Vdau and Kt/Vbcm [1.432(1.235, 1.718) vs 1.434 (1.244, 1.642), P=0.823]. Kt/Vdau was incidentally prone to falsely high values due to operative errors, whereas in these cases OCM-based measurement Kt/Vbcm delivered realistic values. An excellent correlation was observed between Kt/Vdau and Kt/Vbcm; the mean difference was 0.07, 95%CI (-0.66 - 0.79); the correlation coefficient was 0.842(0.821 - 0.862). The patients in Kt/Vbcm≥1.27 group had older age, lower body mass index (BMI), lower height and weight, lower total body water (TBW), lower extracellular water, lower intracellular water, and lower lean tissue index (LTI) compared to those in Kt/Vbcm<1.27 group. Excellent correlations were observed between Kt/Vbcm and TBW or LTI (r=-0.834, P<0.001; r=-0.721, P<0.001). ROC curve analysis showed that the sensitivity and specificity of predicting inadequate delivery of hemodialysis were 87.1% and 86.5%, with a threshold of 30 L for TBW. It also showed that the sensitivity and specificity of predicting inadequate delivery of hemodialysis were 60.4% and 94.6%, with a threshold of 11.05 kg/m2 for LTI. Conclusions BCM can give more accurate parameters of urea distribution volume, thus modifying the result of Kt/V. TBW and LTI are important risk influencing factors for inadequately dialysis, and special attention should be paid to patients with TBW>30 L or LTI>11.05 kg/m2. Key words: Renal dialysis; Body composition; Risk factors; Adequacy of dialysis; Total body water; Lean tissue index