Creatinine generation from kinetic modeling with or without postdialysis serum creatinine measurement: results from the HEMO study

The uric acid-urea distribution volume ratio is a potential marker of hydration status in patients on hemodialysis

The distribution volume of uric acid is affected by the amount of extracellular water (ECW), while urea distribution volume can be considered as total body water (TBW). Thus, the ratio of distribution volumes of uric acid and urea can be paralleled to and be considered as the proxy of ECW/TBW. A total of 108 patients at our facility was included. The uric acid and urea distribution volume ratio (UUVdR) calculated from the single-pool model, which was measured within 1 month of the time when the bioimpedance index was measured. ECW/TBW at the end of the HD session was measured by InBody S10. We investigated the association between the UUVdR and the ECW/TBW values and the factors affecting the residuals of the regression equation. We also evaluated the predictive ability of overhydration or dehydration in randomly selected two groups, i.e., the training group and the validation group. ECW/TBW correlated highly with UUVdR. Multivariate analysis demonstrated that only creatinine and ECW/TBW were significantly associated with regression residuals. The cutoff values of UUVdR for overhydration and dehydration were 0.666 and 0.579, respectively, in the training group. Their AUC were 0.872 and 0.898, respectively. The sensitivity and specificity values in the validation group were 0.571 and 0.868 for overhydration, and 0.444 and 0.953 for dehydration, respectively. UUVdR might be a proxy of hydration status in hemodialysis patients. It may be possible to predict hydration status without dedicated devices in the epidemiological study.

Residual Renal Phosphate Clearance in Patients Receiving Hemodialysis or Hemodiafiltration

OBJECTIVES

Substantial levels of residual renal clearance and urine output may occur in patients treated with hemodialysis or hemodiafiltration. However, the relationships among residual renal urea, creatinine, and phosphate clearances, respectively, and between clearances and urine volume have not been well described.

METHODS

We performed a prospective, cross-sectional study which enrolled hemodialysis and hemodiafiltration patients with a urine volume of >100 mL/day, in whom at least 2 residual renal clearances were obtained over a 6-month observation period. Urine was collected for 24 hours prior to the midweek treatment session and concentrations of urea, creatinine, and phosphate were measured.

RESULTS

Thirty-eight patients (24 men, 14 women) with a mean age of 70.4 ± 12.4 (SD) years were included in this analysis. All patients were dialyzed 3 times per week with mean treatment duration of 243 ± 7.89 minutes. Twenty patients were undergoing hemodiafiltration and 18 patients high-flux hemodialysis. In total, 102 dialysis sessions, of which 52 were hemodiafiltration, and urine collections were analyzed. Mean urine volume was 457 ± 254 mL per 24 hours. Residual renal clearance rates of urea (Kr Urea), creatinine (Kr Cr), and phosphate (Kr Phos) were 1.60 ± 0.979, 4.69 ± 3.79, and 1.98 ± 1.36 mL/minute, respectively. Mean ratios of Kr Cr/Kr Urea, Kr Phos/Kr Urea, and Kr Phos/Kr Cr were 2.83 ± 1.21, 1.23 ± 0.387, and 0.477 ± 0.185, respectively. There was a modest correlation between Kr Phos and daily urine volume (r = 0.605, P = .001).

CONCLUSIONS

In maintenance hemodialysis and hemodiafiltration patients, residual renal phosphate clearance is approximately 23% higher than residual renal urea clearance. Urine volume is a modestly accurate surrogate for estimating residual renal phosphate clearance, but only when urine volume is <300 mL/day.

Urinary deoxynivalenol as a biomarker of exposure in different age, life stage and dietary practice population groups

The Fusarium mycotoxin deoxynivalenol (DON) and its modified forms are present in most samples of grain and grain-based products. Due to the widespread presence of DON in these highly consumed food commodities, nearly all individuals are exposed to DON. Previous estimates of the dietary DON intake in Norway indicated that children's dietary intake is close to or exceed the TDI of 1 µg/kg bw/day for the sum of DON and three modified forms. One aim of the current study was to determine whether the concentrations of DON in morning urine differ between population groups like men, women, children, vegetarians, and pregnant women. An additional aim was to compare a set of models for estimating the dietary intake of DON based on urinary DON concentrations and also compare these models with DON-intakes estimated using food consumption data. DON and metabolites were detected in the morning urine from 256 out of 257 individuals and with concentrations in similar range as reported from other countries. Children have higher urinary DON-concentration than adults and elderly. The urinary DON-concentration in pregnant women and vegetarians did not differ from other adults. The estimated intake of DON was higher for children than for other age groups on a body weight basis. The correlations between different models for estimating DON-intake based on urinary concentration as well as based on individual food consumption were good (0.79-0.99), but with some outliers. We conclude that Norwegians are exposed to DON in the same range as reported from other countries and that children have a higher exposure than adults. Furthermore, we conclude that intake estimates based on urinary DON concentration is a useful tool for evaluation of the exposure at population level, but due to outliers, the estimates for individuals are uncertain. There are also uncertainties in intake estimates both from food consumption and from urinary DON concentration, and we could not conclude on which approach provides the most accurate exposure estimate.

Creatinine generation rate can detect sarcopenia in patients with hemodialysis

BACKGROUND

Sarcopenia is strongly associated with long-term mortality in patients undergoing hemodialysis. The diagnostic modalities used to assess muscle mass, such as bioimpedance analysis and dual-energy X-ray absorption measurement, have limitations for application in patients on hemodialysis. Therefore, there is a need to establish a simple index for assessing muscle mass that can be universally performed in patients on hemodialysis.

METHODS

Patients on maintenance hemodialysis were included in this study. Laboratory tests, skeletal muscle mass measured by bioimpedance analysis, and clinical records were obtained retrospectively. The creatinine generation rate (CGR) was calculated from the pre- and postdialysis blood tests using a kinetic model as the index for whole-body muscle mass. Correlations between the CGR and skeletal muscle mass were investigated, and the cut-off value for muscle wasting was determined. Kaplan-Meier survival analysis was performed to investigate the feasibility of the CGR for predicting long-term survival.

RESULTS

Among the 130 patients included, eight were diagnosed with sarcopenia by bioimpedance analysis. The CGR was positively correlated with skeletal muscle mass (r = 0.454, p < 0.001). Multiple linear regression analysis revealed that age and sex independently influenced the CGR. The patients were classified into two groups according to age- and sex-adjusted CGRs. During a median follow-up period of 32 months, the Kaplan-Meier survival analysis showed that patients with low CGR showed significantly poor long-term prognosis (p = 0.002).

CONCLUSION

The CGR is a simple index for muscle mass and can predict long-term mortality in patients on hemodialysis.

Comparison of Simplified Creatinine Index and Systemic Inflammatory Markers for Nutritional Evaluation of Hemodialysis Patients

Protein-energy wasting (PEW) is associated with adverse outcomes in hemodialysis patients. This study compares the simplified creatinine index (SCI) and circulating inflammatory markers as nutritional screening tools for hemodialysis patients. Maintenance hemodialysis patients (230 total patients, 34.8% women, 64.0 ± 14.3 years old) from a tertiary medical center were assessed for demographic data, body composition analysis, biochemistry tests, and circulating inflammatory biomarkers. The SCI was calculated using Canaud’s formula. Reduced fat-free mass index (FFMI), a surrogate of lean body mass, was identified according to the European Society for Clinical Nutrition and Metabolism guidelines. Nutritional status was assessed by the geriatric nutritional risk index (GNRI) and International Society of Renal Nutrition and Metabolism (ISRNM) criteria. Multivariate logistic regression revealed independent risk factors for low FFMI and malnutrition. Of the patients, 47.4% had low FFMI. Patients with a reduction in FFMI tended to be older females with lower body mass index, SCI, and GNRI scores but significantly higher levels of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), and IL-8. SCI was found to be an independent predictor for reduced FFMI (OR 0.57, 95% CI 0.40–0.81) and presence of PEW according to ISRNM criteria (OR 0.38, 95% CI 0.21–0.68). Although a positive association between systemic inflammatory markers and low FFMI was observed, this association disappeared in multivariate analysis. Moreover, the inflammatory markers examined in this study were not associated with malnutrition after adjusting for potential confounders. Compared with markers of systemic inflammation, SCI achieved better performance in assessing the nutritional status of hemodialysis patients.

Clinical and predictive value of simplified creatinine index used as muscle mass surrogate in end-stage kidney disease haemodialysis patients-results from the international MONitoring Dialysis Outcome initiative

Background

Protein-energy wasting, muscle mass (MM) loss and sarcopenia are highly prevalent and associated with poor outcome in haemodialysis (HD) patients. Monitoring of MM and/or muscle metabolism in HD patients is of paramount importance for timely detection of muscle loss and to intervene adequately. In this study we assessed the reliability and reproducibility of a simplified creatinine index (SCI) as a surrogate marker of MM and explored its predictive value on outcome.

Method

We included all in-centre HD patients from 16 European countries with at least one SCI. The baseline period was defined as 30 days before and after the first multifrequency bioimpedance spectroscopy measurement; the subsequent 7 years constituted the follow-up. SCI was calculated by the Canaud equation. Multivariate Cox proportional hazards models were applied to assess the association of SCI with all-cause mortality. Using backward analysis, we explored the trends of SCI before death. Bland–Altman analysis was performed to analyse the agreement between estimated and measured MM.

Results

We included 23 495 HD patients; 3662 were incident. Females and older patients have lower baseline SCI. Higher SCI was associated with a lower risk of mortality [hazard ratio 0.81 (95% confidence interval 0.79–0.82)]. SCI decline accelerated ∼5–7 months before death. Lean tissue index (LTI) estimated by SCI was correlated with measured LTI in both sexes (males: R² = 0.94; females: R² = 0.92; both P < 0.001). Bland–Altman analysis showed that measured LTI was 4.71 kg/m² (±2 SD: −12.54–3.12) lower than estimated LTI.

Conclusion

SCI is a simple, easily obtainable and clinically relevant surrogate marker of MM in HD patients.

Evaluation of Residual Kidney Function during Once-Weekly Incremental Hemodialysis

BACKGROUND

The initial once-weekly administration of incremental hemodialysis to patients with residual kidney function (RKF) has recently attracted considerable interest.

METHODS

The aim of our study was to assess the performance of a series of different methods in measuring serum urea nitrogen and serum Cr (sCr) RKF in patients on once-weekly hemodialysis (1WHD). Evaluations were carried out by means of 24-h predialysis urine collection (Kr-24H) or 6-day inter-dialysis collection (Kr-IDI) and estimation of glomerular filtration rate based on (KrSUN + KrsCr)/2 for the purpose of identifying a simple reference calculation to be used in assessing RKF in patients on 1WHD dialysis. Ninety-five urine samples were collected from 12 1WHD patients. A solute solver urea and Cr kinetic modeling program was used to calculate residual urea and Cr clearances. Mann-Whitney U test, Pearson's correlation coefficient (R), and linear determination coefficient (R2) were used for statistical analysis.

RESULTS

1WHD patients displayed a mean KrSUN-IDI of 4.5 ± 1.2 mL/min, while KrSUN-24H corresponded to 4.1 ± 0.9 mL/min, mean KrsCr-IDI to 9.1 ± 4.0 mL/min, and KrsCr 24H to 8.9 ± 4.2 mL/min, with a high regression between IDI and 24-h clearances (for IDI had R2 = 0.9149 and for 24H had R2 = 0.9595). A good correlation was also observed between KrSUN-24H and (KrSUN + KrsCR/2) (R2 = 0.7466, p < 0.01.

DISCUSSION

Urine collection over a 24-h predialysis period yielded similar results for both KrSUN and KrsCr compared to collection over a longer interdialytic interval (KrSUN + KrsCr)/2 could be applied to reliably assess RKF in patients on 1WHD.

CONCLUSION

The parameters evaluated are suitable for use as a routine daily method indicating the commencement and continued use of the 1WHD Incremental Program.

Equations to Estimate the Normalized Creatinine Generation Rate (CGRn) in 3/Week Dialysis Patients With or Without Residual Kidney Function

OBJECTIVE

Normalized creatinine generation rate (CGRn) can be computed for a variety of dialysis schedules using a recently described kinetic modeling program. However, the availability of estimating equations might facilitate broader study of this metric. We developed equations to estimate CGRn based on modeling and then tested them against modeled CGRn values in the Frequent Hemodialysis Network Nocturnal Trial baseline (3/week) dataset.

DESIGN AND METHODS

We used a "what-if" derivation of a previously published variable volume 2-pool creatinine kinetic model to generate predicted predialysis values of serum creatinine that would result from creatinine generation rates of 250-2000 mg/day in patients with creatinine distribution volumes of 20 to 50 L, dialyzed from 60 to 480 min per treatment three times a week. Then, in patients with residual kidney function, we calculated an "anuric expected predialysis serum creatinine value" before applying the same equations. We then compared estimated CGRn values as predicted by this approach with modeled values in patient data from the Frequent Hemodialysis Network Nocturnal Trial.

RESULTS

The estimating equations for CGRn yielded results similar to those obtained with formal modeling, in both anuric patients and those with residual kidney function, with mean percent error of 0.845 ± 6.15 (SD) in anuric patients, and ‒0.29 ± 4.90 in patients with a mean creatinine clearance of 5.44 ± 4.82 mL/min, with R-squared values of 0.96 in both anuric patients and those with residual renal clearance of creatinine.

CONCLUSIONS

In patients dialyzed 3/week, CGRn can be estimated using prediction equations. Use of these equations may facilitate broader investigation of CGRn as a measure of nutritional status and outcome.