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Estimating residual kidney function in dialysis patients without urine collection.

ABSTRACT: Residual kidney function contributes substantially to solute clearance in dialysis patients but cannot be assessed without urine collection. We used serum filtration markers to develop dialysis-specific equations to estimate urinary urea clearance without the need for urine collection. In our development cohort, we measured 24-hour urine clearances under close supervision in 44 patients and validated these equations in 826 patients from the Netherlands Cooperative Study on the Adequacy of Dialysis. For the development and validation cohorts, median urinary urea clearance was 2.6 and 2.4 ml/min, respectively. During the 24-hour visit in the development cohort, serum ?-trace protein concentrations remained in steady state but concentrations of all other markers increased. In the validation cohort, bias (median measured minus estimated clearance) was low for all equations. Precision was significantly better for ?-trace protein and ?2-microglobulin equations and the accuracy was significantly greater for ?-trace protein, ?2-microglobulin, and cystatin C equations, compared with the urea plus creatinine equation. Area under the receiver operator characteristic curve for detecting measured urinary urea clearance by equation-estimated urinary urea clearance (both 2 ml/min or more) were 0.821, 0.850, and 0.796 for ?-trace protein, ?2-microglobulin, and cystatin C equations, respectively; significantly greater than the 0.663 for the urea plus creatinine equation. Thus, residual renal function can be estimated in dialysis patients without urine collections.

SUBMITTER: Shafi T

PROVIDER: S-EPMC4834223 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Estimating residual kidney function in dialysis patients without urine collection.

Shafi Tariq T Michels Wieneke M WM Levey Andrew S AS Inker Lesley A LA Dekker Friedo W FW Krediet Raymond T RT Hoekstra Tiny T Schwartz George J GJ Eckfeldt John H JH Coresh Josef J

Kidney international 20160121 5

Residual kidney function contributes substantially to solute clearance in dialysis patients but cannot be assessed without urine collection. We used serum filtration markers to develop dialysis-specific equations to estimate urinary urea clearance without the need for urine collection. In our development cohort, we measured 24-hour urine clearances under close supervision in 44 patients and validated these equations in 826 patients from the Netherlands Cooperative Study on the Adequacy of Dialys ...[more]

PMID: 26924062

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Project description:BackgroundResidual Kidney Function (RKF) is associated with survival benefits in haemodialysis (HD) but is difficult to measure without urine collection. Middle molecules such as Cystatin C and ?2-microglobulin accumulate in renal disease and plasma levels have been used to estimate kidney function early in this condition. We investigated their use to estimate RKF in patients on HD.DesignCystatin C, ?2-microglobulin, urea and creatinine levels were studied in patients on incremental high-flux HD or hemodiafiltration(HDF). Over sequential HD sessions, blood was sampled pre- and post-session 1 and pre-session 2, for estimation of these parameters. Urine was collected during the whole interdialytic interval, for estimation of residual GFR (GFRResidual = mean of urea and creatinine clearance). The relationships of plasma Cystatin C and ?2-microglobulin levels to GFRResidual and urea clearance were determined.ResultsOf the 341 patients studied, 64% had urine output>100 ml/day, 32.6% were on high-flux HD and 67.4% on HDF. Parameters most closely correlated with GFRResidual were 1/?2-micoglobulin (r2 0.67) and 1/Cystatin C (r2 0.50). Both these relationships were weaker at low GFRResidual. The best regression model for GFRResidual, explaining 67% of the variation, was: GFRResidual = 160.3 · (1/?2m) - 4.2. Where ?2m is the pre-dialysis ?2 microglobulin concentration (mg/L). This model was validated in a separate cohort of 50 patients using Bland-Altman analysis. Areas under the curve in Receiver Operating Characteristic analysis aimed at identifying subjects with urea clearance?2 ml/min/1.73 m2 was 0.91 for ?2-microglobulin and 0.86 for Cystatin C. A plasma ?2-microglobulin cut-off of ?19.2 mg/L allowed identification of patients with urea clearance ?2 ml/min/1.73 m2 with 90% specificity and 65% sensitivity.ConclusionPlasma pre-dialysis ?2-microglobulin levels can provide estimates of RKF which may have clinical utility and appear superior to cystatin C. Use of cut-off levels to identify patients with RKF may provide a simple way to individualise dialysis dose based on RKF.

Project description:Background and objectivesResidual kidney function can be assessed by simply measuring urine volume, calculating GFR using 24-hour urine collection, or estimating GFR using the proposed equation (eGFR). We aimed to investigate the relative prognostic value of these residual kidney function parameters in patients on dialysis.Design, setting, participants, & measurementsUsing the database from a nationwide prospective cohort study, we compared differential implications of the residual kidney function indices in 1946 patients on dialysis at 36 dialysis centers in Korea between August 1, 2008 and December 31, 2014. Residual GFR calculated using 24-hour urine collection was determined by an average of renal urea and creatinine clearance on the basis of 24-hour urine collection. eGFR-urea, creatinine and eGFR β2-microglobulin were calculated from the equations using serum urea and creatinine and β2-microglobulin, respectively. The primary outcome was all-cause death.ResultsDuring a mean follow-up of 42 months, 385 (19.8%) patients died. In multivariable Cox analyses, residual urine volume (hazard ratio, 0.96 per 0.1-L/d higher volume; 95% confidence interval, 0.94 to 0.98) and GFR calculated using 24-hour urine collection (hazard ratio, 0.98; 95% confidence interval, 0.95 to 0.99) were independently associated with all-cause mortality. In 1640 patients who had eGFR β2-microglobulin data, eGFR β2-microglobulin (hazard ratio, 0.98; 95% confidence interval, 0.96 to 0.99) was also significantly associated with all-cause mortality as well as residual urine volume (hazard ratio, 0.96 per 0.1-L/d higher volume; 95% confidence interval, 0.94 to 0.98) and GFR calculated using 24-hour urine collection (hazard ratio, 0.97; 95% confidence interval, 0.95 to 0.99). When each residual kidney function index was added to the base model, only urine volume improved the predictability for all-cause mortality (net reclassification index =0.11, P=0.01; integrated discrimination improvement =0.01, P=0.01).ConclusionsHigher residual urine volume was significantly associated with a lower risk of death and exhibited a stronger association with mortality than GFR calculated using 24-hour urine collection and eGFR-urea, creatinine. These results suggest that determining residual urine volume may be beneficial to predict patient survival in patients on dialysis.

Project description:BACKGROUND AND OBJECTIVES:Residual kidney function contributes to the clearance of antibiotics excreted by the kidneys, lowering the antibiotic concentration, which may adversely affect the treatment of peritoneal dialysis-associated peritonitis. The objective of our study was to examine the relationship between residual kidneyfunction and peritonitis treatment outcomes. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS:Our study included 181 participants who experienced 339 episodes of Gram-positive, Gram-negative, and culture-negative peritoneal dialysis-associated peritonitis at a single centerfrom 2003 to 2010. Episodes were categorized according to participants' urinary creatinine clearance (0, >0-5, and >5 ml/min). The data were analyzed using generalized estimating equation models to determine the covariate-adjusted association between urinary creatinine clearance and treatment failure (defined as relapse or recurrent peritonitis episodes, peritoneal catheter removal, or death from any cause during peritonitis treatment). RESULTS:Among episodes of peritonitis due to Gram-positive organisms or culture-negative infections, those experienced by participants with urinary creatinine clearance >5 ml/min had significantly higher odds of treatment failure than episodes experienced by anuric participants (27 of 80 versus 20 of 119 episodes resulting in treatment failure for creatinine clearance >5 versus 0 ml/min; odds ratio, 6.80; 95% confidence interval, 2.37 to 19.6). Episodes experienced by participants with creatinine clearance >0-5 ml/min also had significantly higher odds of treatment failure than episodes experienced by anuric participants (14 of 64 episodes resulting in treatment failure for creatinine clearance >0-5 ml/min; odds ratio, 2.87; 95% confidence interval, 1.12 to 7.35). The odds of relapse and recurrent peritonitis among participants with creatinine clearance >5 ml/min was also significantly higher compared with in anuric participants (17 of 80 versus 12 of 119 episodes resulting in relapse and recurrence for creatinine clearance >5 versus 0 ml/min; odds ratio, 6.76; 95% confidence interval, 1.90 to 23.8). Among participants with Gram-negative peritonitis, creatinine clearance was significantly associated with neither treatment failure nor relapse and recurrent peritonitis. CONCLUSIONS:Residual kidney function as measured by greater urinary creatinine clearance was associated with treatment failure among participants with Gram-positive and culture-negative peritonitis.

Project description:BackgroundMaintenance hemodialysis is typically prescribed thrice weekly irrespective of a patient's residual kidney function (RKF). We hypothesized that a less frequent schedule at hemodialysis therapy initiation is associated with greater preservation of RKF without compromising survival among patients with substantial RKF.Study designA longitudinal cohort.Setting & participants23,645 patients who initiated maintenance hemodialysis therapy in a large dialysis organization in the United States (January 2007 to December 2010), had available RKF data during the first 91 days (or quarter) of dialysis, and survived the first year.PredictorIncremental (routine twice weekly for >6 continuous weeks during the first 91 days upon transition to dialysis) versus conventional (thrice weekly) hemodialysis regimens during the same time.OutcomesChanges in renal urea clearance and urine volume during 1 year after the first quarter and survival after the first year.ResultsAmong 23,645 included patients, 51% had substantial renal urea clearance (≥3.0mL/min/1.73m(2)) at baseline. Compared with 8,068 patients with conventional hemodialysis regimens matched based on baseline renal urea clearance, urine volume, age, sex, diabetes, and central venous catheter use, 351 patients with incremental regimens exhibited 16% (95% CI, 5%-28%) and 15% (95% CI, 2%-30%) more preserved renal urea clearance and urine volume at the second quarter, respectively, which persisted across the following quarters. Incremental regimens showed higher mortality risk in patients with inadequate baseline renal urea clearance (≤3.0mL/min/1.73m(2); HR, 1.61; 95% CI, 1.07-2.44), but not in those with higher baseline renal urea clearance (HR, 0.99; 95% CI, 0.76-1.28). Results were similar in a subgroup defined by baseline urine volume of 600mL/d.LimitationsPotential selection bias and wide CIs.ConclusionsAmong incident hemodialysis patients with substantial RKF, incremental hemodialysis may be a safe treatment regimen and is associated with greater preservation of RKF, whereas higher mortality is observed after the first year of dialysis in those with the lowest RKF. Clinical trials are needed to examine the safety and effectiveness of twice-weekly hemodialysis.

Project description:BACKGROUND:The prevalence of severe obesity, often considered a contraindication to peritoneal dialysis (PD), has increased over time. However, mortality has decreased more rapidly in the PD population than the hemodialysis (HD) population in the United States. The association between obesity and clinical outcomes among patients with end-stage kidney disease remains unclear in the current era. STUDY DESIGN:Historical cohort study. SETTING & PARTICIPANTS:15,573 incident PD patients from a large US dialysis organization (2007-2011). PREDICTOR:Body mass index (BMI). OUTCOMES:Modality longevity, residual renal creatinine clearance, peritonitis, and survival. RESULTS:Higher BMI was significantly associated with shorter time to transfer to HD therapy (P for trend < 0.001), longer time to kidney transplantation (P for trend < 0.001), and, with borderline significance, more frequent peritonitis-related hospitalization (P for trend = 0.05). Compared with lean patients, obese patients had faster declines in residual kidney function (P for trend < 0.001) and consistently achieved lower total Kt/V over time (P for trend < 0.001) despite greater increases in dialysis Kt/V (P for trend < 0.001). There was a U-shaped association between BMI and mortality, with the greatest survival associated with the BMI range of 30 to < 35kg/m2 in the case-mix adjusted model. Compared with matched HD patients, PD patients had lower mortality in the BMI categories of < 25 and 25 to < 35kg/m2 and had equivalent survival in the BMI category ? 35kg/m2 (P for interaction = 0.001 [vs < 25 kg/m2]). This attenuation in survival difference among patients with severe obesity was observed only in patients with diabetes, but not those without diabetes. LIMITATIONS:Inability to evaluate causal associations. Potential indication bias. CONCLUSIONS:Whereas obese PD patients had higher risk for complications than nonobese PD patients, their survival was no worse than matched HD patients.

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Estimating residual kidney function in dialysis patients without urine collection.

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Estimating residual kidney function in dialysis patients without urine collection.

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