Peritoneal Protein Loss Is Not Associated With Sarcopenia in Peritoneal Dialysis Patients

Peritoneal Protein Loss With Time in Peritoneal Dialysis

Longitudinal evolution of peritoneal protein loss (PPL), a reflection of hydrostatic pressure-driven leak of plasma proteins through the large-pore pathway, is not clear. Time on PD causes loss of mesothelial cells, vasculopathy, and increased thickness of the submesothelial fibrous layer. Are these structural changes associated with progressive increase of PPL, in a parallel with the rise in the D/P creatinine? The aim of the present study was to identify longitudinal changes of PPL over time. This single-center, longitudinal study included 52 peritoneal dialysis (PD) patients with a median follow-up of 26.5 months, evaluated at two different time points with a minimum interval of 6 months. Repeated measures analysis was performed using paired sample t-test or the nonparametric Wilcoxon signed-rank test, depending on the distribution. After a median interval of 15.5 months, lower levels of residual renal function and urine volume, lower Kt/V, and creatinine clearance were found. D/P creatinine and PPL were stable, but a decrease in ultrafiltration was present. Systemic inflammation, nutrition, and volume overload showed no significant change with time on PD. Analysis of a subpopulation with over 48 months between initial and subsequential assessment (n = 11) showed again no difference in inflammation, nutritional and hydration parameters from baseline, but importantly PPL decreased after more than 4 years on PD (mean difference 1.2 g/24, p = 0.033). D/P creatinine and dip of sodium remained unchanged. The absence of deleterious effects of time on PD is reassuring, pointing to the benefit of updated PD prescription, including the standard use of more biocompatible solutions towards membrane preservation and adjusted prescription avoiding overhydration and inflammation while maintaining nutritional status. After controlling for confounders, PPL may act as a biomarker of acquired venous vasculopathy, even if small pore fluid transport rates and free water transport are preserved.

Prediction of the sarcopenia in peritoneal dialysis using simple clinical information: A machine learning-based model

INTRODUCTION

Sarcopenia is associated with significant cardiovascular risk, and death in patients undergoing peritoneal dialysis (PD). Three tools are used for diagnosing sarcopenia. The evaluation of muscle mass requires dual energy X-ray absorptiometry (DXA) or computed tomography (CT), which is labor-intensive and relatively expensive. This study aimed to use simple clinical information to develop a machine learning (ML)-based prediction model of PD sarcopenia.

METHODS

According to the newly revised Asian Working Group for Sarcopenia (AWGS2019), patients were subjected to complete sarcopenia screening, including appendicular skeletal muscle mass, grip strength, and five-time chair stand time test. Simple clinical information such as general information, dialysis-related indices, irisin and other laboratory indices, and bioelectrical impedance analysis (BIA) data were collected. All data were randomly split into training (70%) and testing (30%) sets. Difference, correlation, univariate, and multivariate analyses were used to identify core features significantly associated with PD sarcopenia.

RESULT

12 core features (C), namely, grip strength, body mass index (BMI), total body water value, irisin, extracellular water/total body water, fat-free mass index, phase angle, albumin/globulin, blood phosphorus, total cholesterol, triglyceride, and prealbumin were excavated for model construction. Two ML models, the neural network (NN), and support vector machine (SVM) were selected with tenfold cross-validation to determine the optimal parameter. The C-SVM model showed a higher area under the curve (AUC) of 0.82 (95% confidence interval [CI]: 0.67-1.00), with a highest specificity of 0.96, sensitivity of 0.91, positive predictive value (PPV) of 0.96, and negative predictive value (NPV) of 0.91.

CONCLUSION

The ML model effectively predicted PD sarcopenia and has clinical potential to be used as a convenient sarcopenia screening tool.

Increased Peritoneal Protein Loss and Diabetes: Is There a Link?

Increased peritoneal protein loss has been associated with the fast transport of small molecules, diabetes mellitus (DM), and a reduced survival in patients on peritoneal dialysis (PD), although some studies did not confirm the association with survival. In this single-center retrospective study, we investigated the relationship of baseline peritoneal albumin and protein loss with transport status, comorbidities including DM, and survival in 106 incident PD patients during the period of July 2005–June 2014. Five-year survival rate was determined using Cox-regression analysis. There were not significant differences in D/Pcr or peritoneal protein and albumin loss between diabetics and non-diabetics. In the group of 66 non-diabetics, high and high-average transporters for creatinine had higher values for both peritoneal protein (11.85 ± 6.77 vs. 7.85 ± 4.36 g/day; p = 0.002) and albumin (5.03 ± 2.32 vs. 3.72 ± 1.54 g/day; p = 0.016) loss as compared to slow transporters. However, in the group of 40 diabetics, this association was not observed. Upon multivariable regression analysis, the independent association of D/PCr with peritoneal albumin (β = 0.313; p = 0.008) and protein (β = 0.441; p = 0.001) loss was found only in non-diabetics in whom ultrafiltration also appeared as a significant predictor of peritoneal protein loss (β = 0.330; p = 0.000). A high comorbidity grade, older age, and low serum albumin were associated with mortality, but both peritoneal protein and albumin loss as well as D/Pcr were not determinants of survival. Baseline peritoneal protein and albumin loss was not associated with DM and did not predict survival. The clinical significance of the absence of association between fast peritoneal transport status and peritoneal protein flux in diabetics should be evaluated in a prospective study comprising a greater number of diabetics with evaluation of overhydration as a main inducing variable of protein leak.

Peritoneal Protein Loss, Inflammation, and Nutrition: Refuting Myths

Peritoneal protein loss (PPL) has been correlated with mortality, malnutrition and inflammation. More recently overhydration was brought to the equation. This study aims to review classic and recent factors associated with PPL. Prevalent and incident peritoneal dialysis (PD) patients were included. Dialysate and serum IL-6 was obtained during PET. Hydration and nutritional status were assessed by bio-impedance. Linear regression and Cox regression were performed. The 78 included patients presented median values of PPL 4.8 g/24 h, serum IL-6: 5.1 pg/mL, and IL-6 appearance rate 153.5 pg/min. Mean extracellular water excess (EWexc) was 0.88 ± 0.94 L, and lean body mass index (LBMI) 17.3 ± 2.4 kg/m2. After mean follow-up of 33.9 ± 29.3 months, 12 patients died. Linear univariable analysis showed positive associations between PPL and small solute transport, body composition (LBMI and EWexc), comorbidities and performing CAPD (vs. cycler). PPL correlated positively with dialysate appearance rate of IL-6, but not with serum IL-6. Linear multivariable analysis confirmed positive association between PPL and EWexc (p = 0.012; 95%CI: 4.162–31.854), LBMI (p = 0.008; 95%CI: 1.720–11.219) and performing CAPD (p = 0.023; 95%CI: 4.375–54.190). In survival analysis, no relationship was found between mortality and PPL. Multivariable Cox regression showed Charlson Comorbidity Index (HR: 1.896, 95%CI: 1.235–2.913), overhydration (HR: 10.034, 95%CI: 1.426–70.587) and lower PPL (HR: 0.576, 95%CI: 0.339–0.978) were predictors for mortality. Overhydration, was a strong predictor of PPL, overpowering variables previously reported as determinants of PPL, namely clinical correlates of endothelial dysfunction or local inflammation. PPL were not associated with malnutrition or higher mortality, emphasizing the importance of volume overload control in PD patients.

Peritoneal Protein Loss, Inflammation, and Nutrition: Refuting Myths

Peritoneal protein loss (PPL) has been correlated with mortality, malnutrition and inflammation. More recently overhydration was brought to the equation. This study aims to review classic and recent factors associated with PPL. Prevalent and incident peritoneal dialysis (PD) patients were included. Dialysate and serum IL-6 was obtained during PET. Hydration and nutritional status were assessed by bio-impedance. Linear regression and Cox regression were performed. The 78 included patients presented median values of PPL 4.8 g/24 h, serum IL-6: 5.1 pg/mL, and IL-6 appearance rate 153.5 pg/min. Mean extracellular water excess (EWexc) was 0.88 ± 0.94 L, and lean body mass index (LBMI) 17.3 ± 2.4 kg/m2. After mean follow-up of 33.9 ± 29.3 months, 12 patients died. Linear univariable analysis showed positive associations between PPL and small solute transport, body composition (LBMI and EWexc), comorbidities and performing CAPD (vs. cycler). PPL correlated positively with dialysate appearance rate of IL-6, but not with serum IL-6. Linear multivariable analysis confirmed positive association between PPL and EWexc (p = 0.012; 95%CI: 4.162-31.854), LBMI (p = 0.008; 95%CI: 1.720-11.219) and performing CAPD (p = 0.023; 95%CI: 4.375-54.190). In survival analysis, no relationship was found between mortality and PPL. Multivariable Cox regression showed Charlson Comorbidity Index (HR: 1.896, 95%CI: 1.235-2.913), overhydration (HR: 10.034, 95%CI: 1.426-70.587) and lower PPL (HR: 0.576, 95%CI: 0.339-0.978) were predictors for mortality. Overhydration, was a strong predictor of PPL, overpowering variables previously reported as determinants of PPL, namely clinical correlates of endothelial dysfunction or local inflammation. PPL were not associated with malnutrition or higher mortality, emphasizing the importance of volume overload control in PD patients.

Clinical Significance of Volume Status in Body Composition and Physical Performance Measurements in Hemodialysis Patients

Introduction

This study aimed to evaluate the association between volume status and body composition or physical performance measurements in hemodialysis patients.

Methods

A total of 84 patients were enrolled in this study. The participants were divided into tertiles based on the edema index (extracellular water/total body water): low, middle, and high tertiles. Serum albumin and serum high-sensitivity C-reactive protein levels were measured. The appendicular lean mass index (ALM/Ht², kg/m²) was measured using dual-energy X-ray absorptiometry. The thigh muscle area index (TMA/Ht², cm²/m²) was measured using CT. Extracellular and total body water and phase angles were obtained using bioimpedance analysis. The results of the subjective global assessment (SGA), hand-grip strength (HGS), gait speed (GS), short physical performance battery (SPPB), sit-to-stand for 30-second (STS30) test, timed up and go (TUG), sit-to-stand test performed five times (STS5), and 6-minute walk (6-MW) tests were also evaluated.

Results

On the univariate analysis, the SGA score and phase angle in the high tertile group were the lowest among the three groups. On multivariate analysis, TMA/Ht² and phase angle in the high tertile were the lowest among the three groups. Inverse correlations were observed between edema index and TMA/Ht², SGA score, phase angle, HGS, GS, SPPB, STS30, or 6-MW. Positive correlations were observed between the edema index and the STS5 or TUG test. The sensitivity and specificity for predicting low GS were 34.5 and 89.7%, respectively. The values for predicting low SPPB were 68.0 and 79.7%, respectively.

Conclusion

This study demonstrates that high volume status may be associated with decreased muscle mass and physical performance regardless of inflammatory or nutritional status.