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Introduction: Quantification of peritoneal protein loss (PPL) may be expressed according to a timely collection (24-h measurement or 4-h PET assessment) and as a concentration. The aim of this study was to compare the quantification methods of 24-h and 4-h collections. Methods: This study included 81 prevalent peritoneal dialysis patients. Demographics and clinical and bioelectrical impedance features were registered. PPL was measured (4-h PET and 24-h results) and peritoneal protein clearance was calculated. A linear regression model was performed. Results: Age and continuous ambulatory peritoneal dialysis (compared to cycler) were positively associated with greater PPL on 24-h collections. Neither cardiovascular disease, hypertension, diabetes nor the comorbidity Charlson Index was significantly associated with PPL. There was a consistent univariable relationship with D/P creatinine, whichever sampling method was used. Only 24-h measurements of PPL correlated with body composition variables. In multiple linear regression analysis, D/P creatinine association with PPL stands out. On the other hand, 24-h determinations (in grams or clearance) were associated with overhydration. PET protein quantification was associated with peritoneal creatinine clearance. Discussion/Conclusion: Different methods sign different pathophysiological pathways. PET protein loss quantification should be regarded as a marker of peritoneal membrane intrinsic permeability. Measurements of a 24-h sample might be closer to patients’ clinical status and prognosis, signalizing opportunities for therapy intervention.

BACKGROUND AND AIMS Anemia is a highly prevalent and modifiable comorbidity in patients with chronic kidney disease (CKD), which tends to aggravate as the disease progresses. The economic burden of anemia in CKD is high, and quality of life issues (e.g. fatigue, reduced productivity) is common in these patients. Data on the prevalence and treatment of anemia in CKD stages 3 and 4 (based on the estimated glomerular filtration rate according to KDIGO classification) in Portugal are lacking. The NEFROPOR study aimed to estimate the prevalence of anemia in patients with CKD stage 3 or 4 admitted to a Nephrology consultation between 1 January and 31 March 2017 and characterize anemia treatment in this patient population. METHODS NEFROPOR was a retrospective, multicentric study carried out in 10 Portuguese centers. All patients aged ≥18 years with stage 3 or 4 CKD admitted to a Nephrology consultation in one of those centers between 1 January and 31 March 2017 were invited to participate, and data for up to 24 months after admission were collected from patients’ clinical files. Retrieved data included age, body mass index (BMI), anemia status according to the World Health Organization (WHO) diagnostic criteria, and anemia treatment type and duration. Three assessments of the prevalence anemia were performed: at the time of the first Nephrology visit (presentation), at the first analytical results and the overall prevalence in the study cohort. Statistical analysis was performed in SPSS Statistics (v26) and a 0.05 significance level was adopted. RESULTS A total of 176 patients were included in this study, mostly (61.9%) male, with a median age of 76 years (range, 26–97) and a mean BMI indicative of pre-obesity (28.2; standard deviation, 4.2). CKD stage 3b was predominant (43.2%), followed by stage 4 (32.4%) and stage 3a (24.4%). The most frequent CKD etiologies in this cohort were diabetes (39.8%), followed by arterial hypertension (27.8%) and unknown cause (25.6%). Arterial hypertension was largely the most frequent comorbidity, present in 90.3% of patients, followed by diabetes (54.0%). Although less prevalent, coronary artery disease (18.2%) and congestive heart failure (14.8%) were also identified in this patient population. A total of 44.9% of patients [95% confidence interval (CI), 37.7%–52.3%] had anemia at presentation, which was significantly associated with CKD stage, diabetes, peripheral vascular disease and myocardial infarction comorbidities, and diabetes and unknown CKD etiology. The overall prevalence of anemia in the study cohort was 61.9% (95% CI 54.6%–68.9%), and it was significantly associated with diabetes and peripheral vascular disease comorbidities and with diabetes and primary glomerulonephritis as CKD etiologies. The prevalence of anemia at the first analytical results was 49.4% (95% CI 42.1%–56.8%), and it was significantly associated with CKD stage, diabetes, non-skin cancer, peripheral vascular disease and myocardial infarction comorbidities, and diabetes as CKD etiology. Figure 1 shows the evolution of anemia treatment in this cohort over 24 + months. CONCLUSION The three estimates of the prevalence of anemia in this study were consistent with each other, particularly those for the first visit and first analytical results. The latter were also consistent with evidence in the literature reporting a prevalence of anemia in the population of patients with CKD stages 3 and 4 between 40% and 60%. The overall prevalence of anemia in this study was 12%–15% higher than first visit and first analytical results estimates, in agreement with the fact that this refers to a cumulative prevalence. These data support the need for optimized and individualized treatment strategies for patients with CKD stages 3 and 4, maximizing the efficiency of health-care resource use.

BACKGROUND AND AIMS Cardiovascular disease (CVD) is the leading cause of death in chronic kidney disease patients. The interaction between calcium and magnesium has been associated with several pathophysiological processes that occur in the vessel wall, such as endothelial dysfunction and vascular calcification. The aim of this study was to assess the relationship between calcium-to-magnesium (Ca: Mg) ratio and carotid intima-media thickness (CIMT), a widely used risk marker for CVD in the assessment of subclinical atherosclerosis. This study also aimed to establish the role of the Ca: Mg ratio as a predictor of cardiovascular mortality in haemodialysis (HD). METHOD Prevalent HD patients were enrolled in the longitudinal prospective study in a single tertiary centre. According to CIMT measured through B-mode ultrasound, the patients were divided into two groups: ≥0.9 mm (G1) and RESULTS A total of 120 patients on HD were included with mean age 66.5 ± 13.97 years, 66.7% male. Magnesium (P < 0.001), Ca: Mg ratio (P < 0.001) and Adragão score (P CONCLUSION In our population, the Ca: Mg ratio was a predictor of carotid thickening, so its monitoring can be useful to identify patients at higher cardiovascular risk. The Ca: Mg ratio was further validated as a predictor of cardiovascular mortality in HD patients. More studies are needed to better understand the relationship between this ratio and cardiovascular events.

BACKGROUND AND AIMS Malnutrition–inflammation–atherosclerosis syndrome is common in chronic kidney disease and is associated with high mortality, particularly in dialysis patients. Bioimpedance analysis (BIA) is a simple and non-invasive method for nutritional assessment. The aim of this study was to evaluate the relationship between phase angle (PA) and other nutritional parameters and establish its role as predictor of mortality in peritoneal dialysis (PD) patients. METHOD Prevalent PD patients were enrolled in the longitudinal prospective study in a single tertiary center between 2015 and 2020, with a simultaneous BIA assessment and a modified peritoneal equilibration test. Spearman's correlation test was used to assess relevant clinical associations. Survival analysis was performed using the Kaplan–Meier test and univariate and multivariate Cox analysis to determine the predictive factors of all-cause mortality. RESULTS A total of 49 PD patients were included with mean age 55.9 ± 16.2 years, 57.1% male, Charlson comorbidity index 4.9 ± 2.3, Kt/V 2.5 ± 0.7, with a mean follow-up of 39.9 ± 26.3 months. The Spearman's correlation test showed a very strong positive association between PA and extracellular mass/body cell mass (r = 0.939, P CONCLUSION Lower PA appears to be associated with a decline in nutritional status, so monitoring it can be useful to identify patients at higher risk of malnutrition. PA was also validated as an independent predictor of mortality in our PD patients.

BACKGROUND AND AIMS Peritoneal protein loss has been for many years seen as a detrimental consequence of peritoneal dialysis (PD). Many studies correlated this leakage with mortality, malnutrition and inflammation. More recent knowledge has brought overhydration to this equation. This study aims to review classic and recent factors associated with peritoneal protein clearance and its consequences on overall mortality. METHOD Prevalent and incident PD patients were included. Interleukin 6 (IL-6; dialysate and serum) was obtained during a 3.86% glucose peritoneal equilibration test. Hydration and nutritional status was assessed by bioimpedance. Linear and Cox regression were performed. RESULTS A total of 78 patients were included (54 incident, 24 prevalent), the mean age was 54.6 ± 18.1 years, 65% were males, and the mean follow-up was 33.9 ± 29.3 months. The mean Charlson comorbidity index (CCI) was 4.4 ± 2.4. The residual GFR was 6.7 ± 3.6 mL/min/1.73 m2 and the D/P creatinine 0.65 ± 0.12. The IL-6 concentration in the dialysate was 24.9 ± 30.8 pg/mL and in serum was 37.3 ± 5.1 pg/mL. The phase angle was 5.4 ± 1.1°, overhydration 0.88 ± 0.94 L and peritoneal protein clearance 85.6 ± 54.7 mL/24 h. Overall, eight patients died. Linear univariable analysis showed positive associations between peritoneal protein clearance and (i) small solute transport, as measured by D/P creatinine, (ii) body composition, as measured by phase angle and overhydration and (iii) CCI. The peritoneal protein clearance also correlated positively with dialysate IL-6, but not with serum IL-6. By linear multivariable analysis, using the backward method, a significant positive association between peritoneal protein and overhydration (P In the exploratory survival analysis, no relationship was found between mortality and peritoneal protein clearance. A univariable positive association was shown with serum IL-6 concentration, overhydration and CCI. A higher phase angle was associated with lower mortality. No relationship with dialysate IL-6 or D/P creatinine was found. In this early-stage PD population, with globally preserved residual kidney function, an effect of this variable on mortality was not evident. Cox regression, conditional backward method, showed CCI (OR: 1.896, IC: 1.235–2.913, P = 0.003), overhydration (OR: 10.034, IC: 1.426–70.587, P = 0.021) and peritoneal protein clearance (OR: 0.576, IC: 0.339–0.978, P = 0.041) were predictors for mortality. CONCLUSION A better nutrition status and overhydration are the major determinants of peritoneal protein clearance. The survival analysis showed that mortality is higher in overhydrated patients, with higher CCI, but not with higher peritoneal protein clearance. Inflammation, local or systemic, as assessed by IL-6 concentration, did not reveal to be such a strong prognosis predictor as overhydration in these PD patients.

BACKGROUND AND AIMS FGF-21 is a hepatokine that stimulates glucose uptake through GLUT-1. The presence of this glucose transporter in peritoneal fibroblasts is driven by peritoneal glucose exposure and is related to impaired ultrafiltration, predisposing to overhydration. The study was designed to determine FGF-21 levels in peritoneal effluent and serum, and its possible association with overhydration. METHOD Prevalent and incident peritoneal dialysis (PD) patients without diabetes were included. FGF-21 (dialysate and serum) was obtained during a 3.86% glucose peritoneal equilibration test. Peritoneal glucose load was calculated. The presence or absence of local peritoneal production was assessed by comparing the dialysate to plasma (D/P) ratio of FGF-21 (MW 32 kD) with that of albumin (MW 67 kD). Hydration status was assessed by bioimpedance. Spearman's correlations were performed. RESULTS A total of 58 patients (38 incident, 20 prevalent) were included, mean age 54 years, 67% males, PD duration from 1 to 75 months, mean 10.4. Residual GFR was 6.4 ± 3.5 mL/min/1.73 m2 and D/P creatinine 0.65 ± 0.12. Peritoneal glucose load was 110.5 g/day (range 40.8–226.9). Dialysate FGF-21 was 42.5 ± 47.0 pg/mL and serum FGF-21 943.9 ± 1164.8 pg/mL, giving a D/P ratio of 0.07. D/P albumin was 0.009, indicating that dialysate FGF-21 concentrations can be explained by transport from the circulation, without local peritoneal production. Serum FGF-21 was positively correlated with dialysate FGF-21, extracellular water excess and total peritoneal glucose load (all P CONCLUSION FGF-21 in peritoneal effluent is likely not locally produced, but caused by transport from the circulation. The associations between plasma FGF-21 levels with PD duration, peritoneal glucose load and overhydration, all indicate an effect of peritoneal glucose absorption from the peritoneal cavity into the interstitium with an insulin-independent storage into interstitial adipocytes, where it may stimulate the expression of GLUT-1.

BACKGROUND AND AIMS Recently, a growing number of studies have reported a close relationship between high serum calcium and low serum magnesium with vascular calcification. Endothelial dysfunction and vascular inflammation seem plausible risk factors for enhanced progression of kidney disease nevertheless, the knowledge remains scarce. The aim of this study is to evaluate the role of the calcium/magnesium ratio as a risk factor in CKD progression. METHOD Observational, prospective study involving 693 patients (f = 371, m = 322) with stage 4 and 5 CKD. Patients were divided into two groups, according to the development of end-stage renal disease (ESRD): G1 (n = 541), who did not undergo renal replacement therapy and G2 (n = 152), who had started renal replacement therapy (RRT). Several laboratory parameters were measured: haemoglobin, eGFR (MDRD), albumin, cholesterol, magnesium and mineral metabolism markers (PTH, calcium and phosphorus). Baseline characteristics were analysed and compared using Student%u2019s T-test for continuous variables and chi-squared test for categorical variables. Multivariate Cox regression analysis was used to identify independent factors associated with RRT initiation. A modified Poisson regression with robust error variance was used to estimate the cumulative relative risk for RRT initiation. RESULTS The mean age and estimated glomerular filtration rate (eGFR) of the study population was 70.09 ± 12.51 years and 19.91 ± 8.11 mL/min, respectively. Comparing the two groups, G2 had a significantly lower serum levels of Hb (11.75 versus 10.95 g/dL, P = 0.000), calcium (9.34 versus 8.95 mg/dL, P = 0.000), magnesium (1.92 versus 1.40 mg/dL, P = 0.0001), albumin (4.00 versus 3.88 g/dL, P = 0.03) and cholesterol (183.17 versus 172.39 mg/dL, P = 0.01) and a higher serum levels of phosphorus (3.88 versus 4.69 mg/dL, P = 0.0001), calcium/magnesium ratio (5.73 versus 7.56, P = 0.0001) and PTH (209.71 versus 338.84 pg/mL, P = 0.0001). In univariate Cox regression analysis, age, haemoglobin, eGFR, calcium, magnesium, phosphorus, calcium-magnesium ratio and PTH correlate with onset of RRT, which were further tested using a multivariate COX regression model. The results showed a clear relationship between high levels of phosphorus (HRa = 1.638, P = 0.001) and calcium-magnesium ratio (HRa = 1.292; P = 0.002), and low levels of magnesium (HRa = 0.761, P = 0.005) and eGFR (HRa = 0.934; P = 0.0001) were independent risk factors to start depurative techniques. Additionally, Poisson regression analysis showed that high calcium-magnesium ratios (aPR = 1.986; 95% CI 1.026–3.051; P = 0.002), high phosphorus levels (aPR = 1.607; 95% CI 1.324–1.950; P < 0.0001) and low levels eGFR (aPR = 0.927; 95% CI 0.891–0.964; P < 0.0001) were associated with a cumulative risk for initiation of RRT. CONCLUSION Our results suggest that the calcium/magnesium ratio is an independent predictive factor for the initiation of renal replacement therapy. Further studies are required to validate the use of this novel marker as a predictor of CKD progression.