Acute Treatment Effects on GFR in Randomized Clinical Trials of Kidney Disease Progression

BACKGROUND

Acute changes in GFR can occur after initiation of interventions targeting progression of CKD. These acute changes complicate the interpretation of long-term treatment effects.

METHODS

To assess the magnitude and consistency of acute effects in randomized clinical trials and explore factors that might affect them, we performed a meta-analysis of 53 randomized clinical trials for CKD progression, enrolling 56,413 participants with at least one estimated GFR measurement by 6 months after randomization. We defined acute treatment effects as the mean difference in GFR slope from baseline to 3 months between randomized groups. We performed univariable and multivariable metaregression to assess the effect of intervention type, disease state, baseline GFR, and albuminuria on the magnitude of acute effects.

RESULTS

The mean acute effect across all studies was -0.21 ml/min per 1.73 m2 (95% confidence interval, -0.63 to 0.22) over 3 months, with substantial heterogeneity across interventions (95% coverage interval across studies, -2.50 to +2.08 ml/min per 1.73 m2). We observed negative average acute effects in renin angiotensin system blockade, BP lowering, and sodium-glucose cotransporter 2 inhibitor trials, and positive acute effects in trials of immunosuppressive agents. Larger negative acute effects were observed in trials with a higher mean baseline GFR.

CONCLUSION

The magnitude and consistency of acute GFR effects vary across different interventions, and are larger at higher baseline GFR. Understanding the nature and magnitude of acute effects can help inform the optimal design of randomized clinical trials evaluating disease progression in CKD.

Biased estimation with shared parameter models in the presence of competing dropout mechanisms

Recently, Thomadakis et al. quantified potential sources of bias that can occur when shared parameter (SP) models are used to jointly model longitudinal trends of a biomarker over time (e.g., a slope) and time-to-dropout in an effort to address concerns over possible informative censoring. Although SP models induce no bias under a missingness completely at random dropout mechanism, the authors demonstrate that bias can occur under a missingness at random (MAR) dropout mechanism wherein dropout depends on the observed biomarker data. To address this, the authors propose including the most recent observed marker value within the hazard function for the time-to-dropout portion of an SP model. They demonstrate via a limited simulation that the proposed model minimizes bias under a specific MAR dropout mechanism and a specific missingness not-at-random dropout mechanism. In the present article, we compare and contrast their work with that of previous authors by illustrating via simulation and an example the degree of bias or lack thereof that can occur when applying SP models, particularly, in the presence of competing dropout mechanisms. We propose the use of a competing risk SP model as a means to minimize bias whenever competing dropout mechanisms are suspected assuming the competing mechanisms result from distinct observable causes of dropout.

A Multicenter, Selection-Adjusted Comparison of Patient and Technique Survivals on CAPD and Hemodialysis

Four hundred and eighty CAPD and 373 HD patients started regular dialysis treatment between 1981 and 1987 in 6 dialysis centers. The CAPD patients were 6 years older, on average, than the HD patients and had more complicating conditions (43.3% with 3 or more coexisting risk factors versus 28.9% with coexisting complications). The 7-year patient survival rate was not significantly different. Cox's proportional hazards regression showed that age, cardiovascular disease, cerebrovasculardisease, peripheral vasculardisease, diabetes, malignancy and multisystem disease had significant adverse effects on patient survival. After correcting for the influence of these factors, no significant differences in patient survival were seen. However, after 53.5 years of age, the increase in the risk of death was significantly higher in HD than in CAPD patients. Technique survival was significantly different in the 6 centers and was better for HD than for CAPD. There was no statistically significant difference between CAPD and HD technique survival when peritonitis was eliminated as a cause of failure. Based on this 7 year analysis, CAPD would appear to be an excellent alternative to HD.

Estimating Rates of Recurrent Peritonitis for Patients on CAPO

Recurrent peritonitis is a major complication of Continuous Ambulatory Peritoneal Dialysis (CAPD). As a therapy for patients with end stage renal disease, CAPD entails a continuous interaction between patient and various medical devices. The assumptions one makes regarding this interaction play an essential role when estimating the rate of recurrent peritonitis for a given patient population.

Assuming that each patient has a constant rate of peritonitis, two models for evaluating the risk of recurrent peritonitis are considered. One model, the Poisson probability model, applies when the rate of peritonitis is the same from patient to patient. When this occurs, the frequency of peritoneal infections will be randomly distributed among patients (Corey, 1981). A second model, the negative binomial probability model, applies when the rate of peritonitis varies from one patient to another. In this event, the distribution of peritoneal infections will differ from patient to patient. The poisson model would be applicable when, for example, patients behave similarly with respect to their interactions with the medical devices and with potential risk factors. The negative binomial model, on the other hand, makes allowances for patient differences both in terms of their handling of routine exchanges and in their exposure to various risk factors.

This paper provides methods for estimating the mean peritonitis rate under each model. In addition, “survival” curve estimates depicting the probability of remaining peritonitis free (i.e. “surviving”) over time are provided. It is shown, using data from a multi-center clinical trial, that the risk of peritonitis is best described in terms of survival curves rather than the mean peritonitis rate. For both models, the mean peritonitis rate was found to be 0.85 episodes per year. However, under the negative binomial model, the one-year survival rate, expressed as the percentage of patients remaining free of peritonitis, is 52% as compared with only 42% under the Poisson model. Moreover, the negative binomial model provided a significantly better fit to the observed frequency of peritonitis. These findings suggest that the negative binomial model provides a more realistic and accurate portrayal of the risk of peritonitis and that this risk is not nearly as high as would otherwise be indicated by a Poisson analysis.

Peritoneal Dialysis Kinetic Modeling: Validation in a Multicenter Clinical Study

Objective

To clinically validate the use of a computer-based kinetic model for peritoneal dialysis (PD) by assessing the level of agreement between measured and modeled values of urea and creatinine clearances and ultrafiltration (UF).

Design

An open multicenter observational study.

Patients

There were 111 adult continuous ambulatory peritoneal dialysis (CAPD) patients (47 female, 64 male) in four centers. All patients underwent a four-hour peritoneal equilibration test (PET) using 2.5% dextrose but with variable fill volumes (range: 1 -3 L). Patients with a residual renal function greater than 10 mL/min were excluded.

Main Outcome Measures

Correlations and limits of agreement between measured and modeled values of total weekly urea KTN, total weekly normalized creatinine clearance (L/week/1.73 m2), daily drain volume (L), net ultrafiltration (L), daily peritoneal urea clearance (L/day), and daily peritoneal creatinine clearance (L/day). Measured values were obtained from 24-hour urine and dialysate collections while modeled values were based on results from the PET in combination with the PD ADEQUEST® kinetic program.

Results

The results show there is excellent agreement between measured and modeled urea KTN and creatinine clearances, with concordance correlations of 0.94 and 0.92, respectively. Given the excessive variation and limited range in ultrafiltration values, the concordance correlation between measured and modeled UF was only 0.50. In terms of daily peritoneal clearances and ultrafiltration, the level of precision (i.e., standard deviation) in the differences between modeled and measured values is ±1.05 L/ day for urea clearance, ±1.03 L/day for creatinine clearance, and ±0.919 L/day for ultrafiltration. By contrast, the level of precision (i.e., standard deviation) in the differences between two measured values is estimated to be ±0.979 L/day for urea clearance, ±0.802 L/day for creatinine clearance, and ±0.707 L/day for ultrafiltration. Defining the limits of clinical agreement to be ±2 standard deviations of the differences between two clinically measured 24-hour clearances (or ultrafiltration), we find that 94% of the modeled urea clearances, 87% of the modeled creatinine clearances, and 86% of the modeled ultrafiltration values fall within the limits of clinical agreement.

Conclusion

Data from a carefully performed PET and overnight exchange can, in combination with a scientifically validated kinetic model, provide clinicians with a powerful mathematical tool for use in CAPD dialysis prescription management. Although not intended to replace actual measurements, kinetic modeling can prove useful as a means for predicting clearances for various alternative prescriptions and perhaps also as a means for checking certain types of noncompliance.

The Effect of Technique Failure on Outcome in Black Patients on Continuous Ambulatory Peritoneal Dialysis

Background

We previously reported that, while black patients have a better patient survival than white patients on peritoneal dialysis (PD), they also have a significantly higher technique failure rate (39% vs 8%, p < 0.0001). The purpose of this study was to determine the effect of technique failure/transfer to hemodialysis (HD) on patient survival in black PD patients.

Methods

We retrospectively evaluated 137 incident black patients entering our PD program from January 1987 to December 1997. During the course of follow-up, 82 (60%) patients remained on PD (PD group) while 55 (40%) patients were permanently transferred to HD (PD–HD group). The primary outcome measured was patient survival.

Results

Average age was 49 ± 15 years, 42% were male, and 40% had diabetes mellitus. At baseline, serum creatinine was 10.8 ± 5.4 mg/dL, serum albumin 3.4 ± 0.7 g/dL, body mass index 27.3 ± 6.5 kg/m2, peritoneal transport status was high in 18% and high-average in 61%, and residual glomerular filtration rate was 3.4 ± 3.5 mL/minute. There were no significant differences in clinical features, nutritional status, peritoneal transport, residual renal function, or dialysis adequacy at baseline between the PD group and PD–HD group. While a greater proportion of patients transferring to HD had cardiac disease (53% vs 32%, p < 0.05), there were no other significant differences in 15 comorbid conditions assessed at baseline. The primary reason for transfer was peritonitis (64%) and the overall peritonitis rate in the PD–HD group was significantly higher than in the PD group (2.21 vs 1.17 episodes/patient-year, p < 0.0001). Overall follow-up was 34 ± 25 months for PD group and 44 ± 26 months for PD–HD group ( p < 0.01), with a mean time on PD prior to transfer to HD of 22 ± 18 months. During the course of follow-up, there were no significant differences between the two groups in the number of patients transplanted or deaths. Patient survival at 1, 2, and 5 years was 91%, 80%, and 57% for PD group and 96%, 92%, and 55% for PD–HD group [ p = not significant (NS)]. A risk-adjusted time-dependent Cox regression analysis resulted in an adjusted relative risk of death that was not significantly different for those who transferred from PD to HD versus those who remained on PD (relative risk 1.49; 95% confidence interval 0.77–2.89; p = NS).

Conclusions

In black patients on PD, transfer to HD is not associated with any significant difference in patient survival compared to patients remaining on PD. While a high rate of peritonitis predisposes to technique failure, we found no features at baseline predictive of patients at greatest risk to fail PD. Since technique failure does not portend a poorer prognosis, PD remains a viable option for black patients entering an end-stage renal disease program.

A Multinational Clinical Validation Study of Pd Adequest 2.0

Objective

To clinically validate the use of the newly released kinetic modeling program, PD ADEQUEST 2.0 for Windows (Baxter Healthcare Corporation, Deerfield, IL, U.S.A.), by assessing the level of agreement between measured and modeled values of urea and creatinine clearances (CCr), glucose absorption, total drain volumes, and net ultrafiltration for all forms of peritoneal dialysis.

Design

A nonrandomized, multinational, prospective longitudinal study.

Patients

The study involved 104 adult patients [41 on continuous ambulatory peritoneal dialysis (CAPD), 63 on automated peritoneal dialysis (APD)] from 16 centers in 7 countries. All patients underwent a 4-hour peritoneal equilibration test (PET) but with varying percentage dextrose concentrations (1.5% or 2.5% dextrose) and varying fill volumes (range 1.5 – 2.5 L). Patients with a residual renal function greater than 10 mL/min were excluded, as were patients who had peritonitis within 6 weeks prior to baseline.

Main Outcome Measures

Correlation coefficients and Bland–Altman limits of agreement were used to assess the level of agreement between measured and modeled values of weekly peritoneal urea Kt/V (pKt/V) and total Kt/V, weekly peritoneal creatinine clearance (pCCr, L/week/ 1.73 m2) and total CCr (L/week/1.73 m2), daily drain volume (L/day), net ultrafiltration (UF, L/day), daily peritoneal urea and creatinine mass removal (g/day), and daily peritoneal glucose absorption (g/day). Measured values were obtained from three repeat 24-hour urine and dialysate collections per patient, while modeled values were calculated using the Baxter PD ADEQUEST 2.0 program in conjunction with kinetic parameters estimated from a 4-hour PET and long-dwell exchange independent of the 24-hour collections.

Results

The results show there is excellent agreement between measured and modeled urea Kt/V and CCr with concordance correlation coefficients ranging from 0.83 to 0.97 among CAPD and APD patients. There was also excellent agreement between measured and modeled values of glucose absorption and total drain volumes (concordance correlations of 0.90 and 0.98, respectively). This level of agreement was further supported by a Bland– Altman analysis of individual differences, including differences between measured and modeled net UF (coefficient of clinical agreement ranged from 0.66 to 0.92).

Conclusions

Data from a carefully performed PET and overnight exchange can, in combination with a scientifically and clinically validated kinetic model, provide clinicians with a powerful mathematical tool for use in CAPD and APD prescription management. Although not intended to replace actual measurements, kinetic modeling can prove useful as a means for quickly estimating approximate levels of clearance for a wide variety of alternative prescriptions. This, in turn, should speed up the process by which a physician can optimize the dose of dialysis suitable for a given patient and his/her lifestyle.

Correlation between Peritoneal Equilibration Test and Dialysis Adequacy and Transport Test, for Peritoneal Transport Type Characterization

Objective

The aim of this study was to analyze the correlation between the peritoneal equilibration test (PET) and the dialysis adequacy and transport test (DATT) for peritoneal transport type characterization, and the degree of patients’ acceptance for each test.

Design

Cross-sectional, observational multicenter study.

Setting

Five referral (tertiary) dialysis centers of institutional practice.

Patients

The study included 107 adult continuous ambulatory peritoneal dialysis (CAPD) patients with a prescription of four exchanges of 2 L per day, irrespective of age, gender, cause of end-stage renal disease, time on dialysis, nutritional status, or residual renal function. Patients on immunosuppressive therapy and those with cancer, hepatitis B, or HIV, and those having a peritonitis episode within the previous 30 days, or three or more episodes during the previous 12 months, were excluded.

Main Measures

Peritoneal transport type as classified by creatinine and urea dialysis-to-plasma (D/P) ratios by PET and DATT.

Results

Correlation coefficients between D/P ratios for creatinine and urea, obtained for the PET and the DATT, were 0.73 for D/P creatinine and 0.96 for D/P urea. Patients were classified into high, high-average, low-average, and low transport categories according to the mean and standard deviation of D/P creatinine values obtained from the PET at 4 hours. These values showed excellent concordance with those generated from the DATT data (κ = 0.82, 95% confidence interval 0.67 – 0.93). Nineteen percent of patients showed discordance in their category when classified according to the PET versus the DATT. Patients’ acceptance was better for the DATT than for the PET, as evaluated with a questionnaire.

Conclusion

The DATT is an easy, inexpensive, and reliable test to assess peritoneal transport type, and it also provides information about peritoneal clearance of solutes and ultrafiltration. The DATT has better patient acceptance than the PET. Since the DATT has only been validated for patients on a fixed CAPD daily schedule of 4 x 2 L, the results should be confined only to patients receiving such a prescription.

A Retrospective Assessment of Risk Factors for Peritonitis among An Urban Capd Population

Peritonitis is a major reason why patients transfer from peritoneal dialysis (PD) to hemodialysis. We evaluated the peritonitis infection rates In 146 peritoneal dialysis patients who underwent dialysis at our facility between 1 January 1981 and 31 December 1989. Peritonit Is was the primary cause for changing treatment, with 24 (16.4%) of the patients transferring because of this complication. This represented 54.5% of all patients discontinuing CAPD due to method failure. A gamma-Poisson regression analysis was performed in an attempt to Identify potential risk factors associated with an increased Incidence of peritonitis. The results indicated that race, education level, and PD system used were significantly associated with the rate at which peritonitis occurred in our patient population. There was an almost twofold increase in the rate of peritonitis among blacks as compared to whites (2.2 vs 1.2 episodes/patient year). The level of education completed at the start of dialysis had a negative correlation with peritonitis rates. Patients with ≤8, 9–12, and ≥13 years of education had peritonitis rates of 2.4, 1.8, and 1.2 episodes/patient year, respectively. Finally, the system used had a significant effect with our patients on CCPD having lower peritonitis rates as compared to patients on either a connect or disconnect system (0.6 vs 2.5 vs 1.8 episodes/patient year, respectively). Recognizing potential risk factors for peritonitis will help us better understand and address this significant problem in our PD programs. Reducing peritonitis rates should facilitate a decrease in patient transfer due to method failure.

Modeling of Icodextrin in PD Adequest® 2.0

Objective

To validate the use of a modified three-pore model for predicting fluid transport during long dwell exchanges that use a 7.5% icodextrin solution.

Design

A nonrandomized, single group, repeated measures study.

Patients

Ten peritoneal dialysis patients underwent a single 8-hour exchange of a 7.5% icodextrin solution. All patients were naïve to icodextrin.

Main Outcome Measures

A modified three-pore model was used to model solute and fluid transport during each 8-hour exchange. Concordance correlation coefficients were used to estimate the level of agreement between modeled and measured values of net ultrafiltration (UF) and intraperitoneal volume.

Methods

Each patient underwent a modified 8-hour standard peritoneal permeability analysis using a 2-L 7.5% icodextrin exchange. Dextran 70 was added to the icodextrin solution as volume marker to estimate fluid transport kinetics. Transcapillary UF, fluid absorption, and intraperitoneal volumes were assessed via the volume marker at 0, 5, 15, 30, 60, 120, 240, 300, 360, 420, and 480 minutes.

Results

There was strong agreement (concordance correlation = 0.9856) between net UF as measured by the volume marker data and net UF as modeled using the modified three-pore model implemented in PD Adequest (Baxter Healthcare, Deerfield, Illinois, USA).

Conclusions

Net UF and intraperitoneal volumes for long dwell exchanges using a 7.5% icodextrin solution can be accurately modeled with a modified three-pore model. Steady state icodextrin plasma levels are needed to accurately predict net UF for chronic users of icodextrin.

Performance of GFR Slope as a Surrogate End Point for Kidney Disease Progression in Clinical Trials: A Statistical Simulation

BACKGROUND

Randomized trials of CKD treatments traditionally use clinical events late in CKD progression as end points. This requires costly studies with large sample sizes and long follow-up. Surrogate end points like GFR slope may speed up the evaluation of new therapies by enabling smaller studies with shorter follow-up.

METHODS

We used statistical simulations to identify trial situations where GFR slope provides increased statistical power compared with the clinical end point of doubling of serum creatinine or kidney failure. We simulated GFR trajectories based on data from 47 randomized treatment comparisons. We evaluated the sample size required for adequate statistical power based on GFR slopes calculated from baseline and from 3 months follow-up.

RESULTS

In most scenarios where the treatment has no acute effect, analyses of GFR slope provided similar or improved statistical power compared with the clinical end point, often allowing investigators to shorten follow-up by at least half while simultaneously reducing sample size. When patients' GFRs are higher, the power advantages of GFR slope increase. However, acute treatment effects within several months of randomization can increase the risk of false conclusions about therapies based on GFR slope. Care is needed in study design and analysis to avoid such false conclusions.

CONCLUSIONS

Use of GFR slope can substantially increase statistical power compared with the clinical end point, particularly when baseline GFR is high and there is no acute effect. The optimum GFR-based end point depends on multiple factors including the rate of GFR decline, type of treatment effect and study design.

GFR Slope as a Surrogate End Point for Kidney Disease Progression in Clinical Trials: A Meta-Analysis of Treatment Effects of Randomized Controlled Trials

BACKGROUND

Surrogate end points are needed to assess whether treatments are effective in the early stages of CKD. GFR decline leads to kidney failure, but regulators have not approved using differences in the change in GFR from the beginning to the end of a randomized, controlled trial as an end point in CKD because it is not clear whether small changes in the GFR slope will translate to clinical benefits.

METHODS

To assess the use of GFR slope as a surrogate end point for CKD progression, we performed a meta-analysis of 47 RCTs that tested 12 interventions in 60,620 subjects. We estimated treatment effects on GFR slope (mean difference in GFR slope between the randomized groups), for the total slope starting at baseline, chronic slope starting at 3 months after randomization, and on the clinical end point (doubling of serum creatinine, GFR<15 ml/min per 1.73 m², or ESKD) for each study. We used Bayesian mixed-effects analyses to describe the association of treatment effects on GFR slope with the clinical end point and to test how well the GFR slope predicts a treatment's effect on the clinical end point.

RESULTS

Across all studies, the treatment effect on 3-year total GFR slope (median R ²=0.97; 95% Bayesian credible interval [BCI], 0.78 to 1.00) and on the chronic slope (R ² 0.96; 95% BCI, 0.63 to 1.00) accurately predicted treatment effects on the clinical end point. With a sufficient sample size, a treatment effect of 0.75 ml/min per 1.73 m²/yr or greater on total slope over 3 years or chronic slope predicts a clinical benefit on CKD progress with at least 96% probability.

CONCLUSIONS

With large enough sample sizes, GFR slope may be a viable surrogate for clinical end points in CKD RCTs.

Calculating Standard Kt/V during Hemodialysis Based on Urea Mass Removed

BACKGROUND/AIMS

We derived a novel equation for calculating weekly urea standard Kt/V (stdKt/V) during hemodialysis (HD) based on urea mass removed, comparable to the approach during peritoneal dialysis.

METHODS

Theoretical consideration of urea mass balance during HD led to the following equation for stdKt/V, namely, stdKt/V = N × (URR + UFV/V), where N is the number of treatments per week, URR is urea reduction ratio per treatment, UFV is ultrafiltration volume per treatment, and V is postdialysis urea distribution volume. URR required corrections for postdialysis rebound and intradialytic urea generation. We compared the accuracy of this approach with previous equations for stdKt/V by numerical simulations using a 2-compartment model of urea kinetics for thrice-weekly and more frequent HD prescriptions.

RESULTS

The proposed equation based on urea mass removed predicted values of stdKt/V that are equivalent to those calculated by previous equations for stdKt/V.

CONCLUSION

This work provides a novel approach for calculating stdKt/V during HD and strengthens the theoretical understanding of stdKt/V.

PSA enzymatic activity: a new biomarker for assessing prostate cancer aggressiveness

BACKGROUND

With the advent of widespread prostate-specific antigen (PSA) testing in recent decades, prostate cancer (PCa) has emerged as the most frequently diagnosed non-skin cancer among men in the U.S. and Europe. Greater screening rates coupled with improved detection methods have caused a controversial upsurge in the number of men undergoing prostate biopsy and subsequent treatment. However, current diagnostic techniques generally suffer from limited ability to identify which seemingly indolent cancers are biologically aggressive.

METHODS

We collected prostatic fluid from 778 post-radical prostatectomy specimens and randomly selected samples from both the clinically confirmed aggressive (n = 50) and non-aggressive (n = 50) prostate cancer populations. We measured the level of proteolytic enzyme activity of PSA (aPSA) in each sample and used receiver operating characteristic (ROC) analysis to correlate aPSA levels with prostate cancer aggressiveness.

RESULTS

We found aPSA in prostatic fluid to be inversely proportional to disease stage, such that patients with the most aggressive PCa have on average significantly reduced aPSA compared to those with less aggressive disease. Significantly, our results suggest that many (22% in our study population) of the diagnosed patients with non-aggressive PCa could have averted or delayed radical prostatectomy.

CONCLUSIONS

Given the high level of debate surrounding PSA screening effectiveness [3-5] and the recent U.S. Preventative Services Task Force recommendation to discontinue PSA screening [6], our results provide renewed hope that a clinical monitoring tool may emerge that truly refines PCa treatment decision-making.

What is the true number needed to screen and treat to save a life with prostate-specific antigen testing?

PURPOSE

The European Randomized Study of Screening for Prostate Cancer (ERSPC) reported a 20% mortality reduction with prostate-specific antigen (PSA) screening. However, they estimated a number needed to screen (NNS) of 1,410 and a number needed to treat (NNT) of 48 to prevent one prostate cancer death at 9 years. Although NNS and NNT are useful statistics to assess the benefits and harms of an intervention, in a survival study setting such as the ERSPC, NNS and NNT are time specific, and reporting values at one time point may lead to misinterpretation of results. Our objective was to re-examine the effect of varying follow-up times on NNS and NNT using data extrapolated from the ERSPC report.

MATERIALS AND METHODS

On the basis of published ERSPC data, we modeled the cumulative hazard function using a piecewise exponential model, assuming a constant hazard of 0.0002 for the screening and control groups for years 1 to 7 of the trial and different constant rates of 0.00062 and 0.00102 for the screening and control groups, respectively, for years 8 to 12. Annualized cancer detection and drop-out rates were also approximated based on the observed number of individuals at risk in published ERSPC data.

RESULTS

According to our model, the NNS and NNT at 9 years were 1,254 and 43, respectively. Subsequently, NNS decreased from 837 at year 10 to 503 at year 12, and NNT decreased from 29 to 18.

CONCLUSION

Despite the seemingly simplistic nature of estimating NNT, there is widespread misunderstanding of its pitfalls. With additional follow-up in the ERSPC, if the mortality difference continues to grow, the NNT to save a life with PSA screening will decrease.

Assessing creatinine clearance from modification of diet in renal disease study equations in the ADEMEX cohort: limitations and potential applications

BACKGROUND AND OBJECTIVES

Twenty-four-hour urine and dialysate collections provide accepted means to assess adequacy in peritoneal dialysis (PD). Recent publications suggest that creatinine clearance (CrCl) estimated from the Modification of Diet in Renal Disease (MDRD) equations (eCrCl) accurately approximates measured CrCl (mCrCl) derived from 24-hour collections of urine and dialysate and might serve as an alternative means to assess small-solute clearance and adequacy in PD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Post hoc analysis of data from patients enrolled in ADEMEX was used to assess agreement between mCrCl and eCrCl derived by four- and six-variable MDRD equations (4V-MDRDE and 6V-MDRDE, respectively). Additionally, associations among mCrCl, eCrCl, and survival were determined.

RESULTS

Acceptable precision was observed between mCrCl and 4V-MDRDE-eCrCl and 6V-MDRDE-eCrCl for the entire cohort. Precision was markedly diminished when analysis was limited to functionally anuric patients with mCrCl < 12 ml/min per 1.73 m². Although there was no association between survival and mCrCl, for every 1-ml/min per 1.73 m² increase in 4V- and 6V-MDRDE-eCrCl, there was a 6% and 4% increase in risk of death, respectively. There was a negative association between MDRDE-eCrCl and creatinine appearance rates, suggesting MDRDE-eCrCl is significantly confounded by individual differences in muscle mass.

CONCLUSIONS

MDRDE-eCrCl provides demographically comparable values to 24-hour urine and dialysate collections across the ADEMEX cohort. However, MDRDEs should not be used to assess small-solute removal or adequacy in individual PD patients or to predict outcome in any cohort of patients over narrow ranges of limited clearance.

Effects of radiotherapy with or without chemotherapy on tongue strength and swallowing in patients with oral cancer

BACKGROUND

Oral tongue strength and swallowing ability are reduced in patients treated with chemoradiotherapy for oral and oropharyngeal cancer.

METHODS

Patients with oral or oropharyngeal cancer treated with high-dose chemoradiotherapy underwent tongue strength, swallowing, and dietary assessments at pretreatment and 1, 3, 6, and 12 months posttreatment. Tongue strength was assessed using the Iowa Oral Performance Instrument (IOPI). Oral and pharyngeal residue was evaluated utilizing videofluoroscopy.

RESULTS

Mean maximum tongue strength dropped a nonsignificant amount immediately after treatment, and then increased significantly at 6- and 12-months posttreatment completion. Analyses were adjusted for patient dropout. Tongue strength was not significantly correlated with swallow observations of percentage oral and pharyngeal residue. Ability to eat various diet consistencies was reduced after treatment but improved over time at a rate similar to changes in oral intake and type of diet.

CONCLUSIONS

Parallel but not significant changes in oral intake, diet, and tongue strength in the first year post chemoradiation therapy need further study in a larger population.

Mortality studies comparing peritoneal dialysis and hemodialysis: what do they tell us?

Several recent large-scale epidemiological studies comparing mortality among end-stage renal disease (ESRD) patients receiving hemodialysis (HD) versus peritoneal dialysis (PD) show conflicting results. In this paper, we undertake a critical review of these studies. Our goal is to determine if there are any consistent trends in outcomes between HD and PD within select subgroups of patients once methodological differences have been accounted for. A total of six large-scale registry studies and three prospective cohort studies conducted in the United States (US), Canada, Denmark, and the Netherlands were reviewed. Summary findings from these studies are presented for comparative purposes. Additional summary analyses based on previously reported data on 398 940 incident US Medicare patients are included for the purpose of comparing results from this population of patients to those of the other select studies when similar methods of analysis are applied. Results are summarized in terms of the relative risk of death for PD versus HD (RR[PD:HD]). Differences in results between the nine studies can be attributed to the degree of case-mix adjustment carried out and to the use of different subgroups when comparing mortality between HD and PD. When these differences are accounted for, we found a remarkable degree of synergism in results between the registry studies and, to a lesser degree, the prospective cohort studies. PD was generally found to be associated with equal or better survival among non-diabetic patients and younger diabetic patients in all four countries. However, among older diabetic patients, results varied by country. The Canadian and Danish registries showed no difference in survival between PD and HD among older diabetics while in the US, HD was associated with better survival for diabetics aged 45 and older. All studies show a time-dependent trend in the RR of death with PD generally associated with equivalent or better survival during the first year or two of dialysis. However, results on longer-term survival varied according to study and to different subgroups within studies. Subgroup analyses in the prospective cohort studies were limited by small numbers of patients resulting in highly varied and somewhat controversial results when compared to the larger registry-based studies. Based on our review of recent publications and additional analyses of US Medicare data, we conclude that overall patient survival is similar for PD and HD but that important differences do exist within select subgroups of patients, particularly those subgroups defined by age and the presence or absence of diabetes.

The reverse epidemiology of plasma total homocysteine as a mortality risk factor is related to the impact of wasting and inflammation

BACKGROUND

The reason(s) for the apparently paradoxical 'reverse' association in end-stage renal disease (ESRD) patients in whom a low, rather than a high, total plasma total homocysteine (tHcy) level is an indicator of poor outcome remains unclear. The aim of this study was to examine whether the inverse association maintains, mitigates or reverses after comprehensive multivariate adjustment for the presence of wasting and inflammation as well as other potential confounders.

METHODS

We studied 317 ESRD patients starting dialysis therapy. Fasting blood samples were taken for the analyses of tHcy, serum albumin, C-reactive protein (CRP), serum creatinine and plasma folate. Nutritional status was assessed by subjective global assessment (SGA). Survival was followed for up to 66 months; 105 patients died.

RESULTS

Using Kaplan-Meier analysis, a low tHcy concentration (< or =30 micromol/l) was associated with higher all-cause and cardiovascular (CV) mortality (P < 0.05). Using Cox proportional analysis adjusting for age, gender, glomerular filtration rate = GFR, cardiovascular disease = CVD, plasma folate, total cholesterol and diabetes mellitus, the all-cause and CV mortality still tended to be high for patients with low tHcy. Adding nutritional and inflammation markers (Body mass index = BMI, SGA, serum creatinine, serum albumin and CRP), a low tHcy level was no longer associated with higher mortality but a trend for high tHcy was observed.

CONCLUSIONS

The link between wasting inflammation and a low tHcy appears to be responsible for the reverse association between plasma tHcy and clinical outcome in ESRD patients. After adjustment for confounders including nutritional and inflammation markers, a trend towards increased death risk for high, rather than low, tHcy levels was apparent after adjustment.

Modeling of icodextrin in PD Adequest 2.0

OBJECTIVE

To validate the use of a modified three-pore model for predicting fluid transport during long dwell exchanges that use a 7.5% icodextrin solution.

DESIGN

A nonrandomized, single group, repeated measures study.

PATIENTS

Ten peritoneal dialysis patients underwent a single 8-hour exchange of a 7.5% icodextrin solution. All patients were naive to icodextrin.

MAIN OUTCOME MEASURES

A modified three-pore model was used to model solute and fluid transport during each 8-hour exchange. Concordance correlation coefficients were used to estimate the level of agreement between modeled and measured values of net ultrafiltration (UF) and intraperitoneal volume.

METHODS

Each patient underwent a modified 8-hour standard peritoneal permeability analysis using a 2-L 7.5% icodextrin exchange. Dextran 70 was added to the icodextrin solution as volume marker to estimate fluid transport kinetics. Transcapillary UF, fluid absorption, and intraperitoneal volumes were assessed via the volume marker at 0, 5, 15, 30, 60, 120, 240, 300, 360, 420, and 480 minutes.

RESULTS

There was strong agreement (concordance correlation = 0.9856) between net UF as measured by the volume marker data and net UF as modeled using the modified three-pore model implemented in PD Adequest (Baxter Healthcare, Deerfield, Illinois, USA).

CONCLUSIONS

Net UF and intraperitoneal volumes for long dwell exchanges using a 7.5% icodextrin solution can be accurately modeled with a modified three-pore model. Steady state icodextrin plasma levels are needed to accurately predict net UF for chronic users of icodextrin.

Estrogen and Progesterone Levels in Nipple Aspirate Fluid of Healthy Premenopausal Women: Relationship to Steroid Precursors and Response Proteins

BACKGROUND

Concentrations of estrogen and progesterone within the breast could provide a better reflection of breast cancer risk than levels in the circulation. We developed highly sensitive immunoassays for multiple steroid hormones and proteins in the nipple aspirate fluid (NAF), which can be obtained noninvasively with a simple suction device. Previous studies showed that NAF hormone levels are strongly correlated between breasts and within a single breast over time and are predictably related to hormone replacement therapy or use of oral contraceptives. This study evaluates the relationship of NAF estrogen and progesterone levels to those in serum and saliva, the relationship of NAF estradiol to androgenic and estrogenic precursors in NAF, and the relationship of NAF hormone levels to those of response proteins such as cathepsin D and epidermal growth factor (EGF).

METHODS

Normal premenopausal women collected saliva daily and donated blood and NAF in the midluteal phases of menstrual cycles at intervals of 0, 4, 12, and 15 months. Analytes were measured by immunoassays after solvent fractionation. Log-transformed values were fit to repeated measures analysis of covariance models to ascertain associations between analytes.

RESULTS

Small nonsignificant associations were found between NAF and serum or salivary estradiol. However, progesterone in NAF was significantly associated with progesterone in serum and saliva (R=0.18 and 0.32, respectively). Within NAF, the estradiol precursors estrone sulfate, androstenedione, and dehydroepiandrosterone were significantly associated with estradiol concentration (P<0.06), and a multiprecursor model explained the majority of variance in NAF estradiol (model R(2)=0.83). Cathepsin D and EGF in NAF could not be predicted from serum or salivary steroid measurements; however, both could be predicted from estradiol and its precursors in NAF (model R(2)=0.70 and 0.93, respectively).

CONCLUSIONS

By showing consistent associations between estradiol and its precursors and response proteins, these data provide support for the biological validity of NAF hormone measurements and for the importance of steroid interconversion by aromatase and sulfatase within the breast. The low correlation between estrogen levels in NAF and those in serum or saliva suggests that the degree of association between estrogen or its androgen precursor levels and risk of breast cancer observed in epidemiologic studies using serum estimates might be highly attenuated.

Shared parameter models for the joint analysis of longitudinal data and event times

Longitudinal studies often gather joint information on time to some event (survival analysis, time to dropout) and serial outcome measures (repeated measures, growth curves). Depending on the purpose of the study, one may wish to estimate and compare serial trends over time while accounting for possibly non-ignorable dropout or one may wish to investigate any associations that may exist between the event time of interest and various longitudinal trends. In this paper, we consider a class of random-effects models known as shared parameter models that are particularly useful for jointly analysing such data; namely repeated measurements and event time data. Specific attention will be given to the longitudinal setting where the primary goal is to estimate and compare serial trends over time while adjusting for possible informative censoring due to patient dropout. Parametric and semi-parametric survival models for event times together with generalized linear or non-linear mixed-effects models for repeated measurements are proposed for jointly modelling serial outcome measures and event times. Methods of estimation are based on a generalized non-linear mixed-effects model that may be easily implemented using existing software. This approach allows for flexible modelling of both the distribution of event times and of the relationship of the longitudinal response variable to the event time of interest. The model and methods are illustrated using data from a multi-centre study of the effects of diet and blood pressure control on progression of renal disease, the modification of diet in renal disease study.

The differential impact of risk factors on mortality in hemodialysis and peritoneal dialysis

BACKGROUND

While the survival ramifications of dialysis modality selection are still debated, it seems reasonable to postulate that outcome comparisons are not the same for all patients at all times. Trends in available data indicate the relative risk of death with hemodialysis (HD) compared to peritoneal dialysis (PD) varies by time on dialysis and the presence of various risk factors. This study was undertaken to identify key patient characteristics for which the risk of death differs by dialysis modality.

METHODS

Analyses utilized incidence data from 398,940 United States Medicare patients initiating dialysis between 1995 and 2000. Proportional hazards regression identified the presence of diabetes, age, and the presence of comorbidity as factors that significantly interact with treatment modality. Stratifying by these factors, proportional and nonproportional hazards models were used to estimate relative risks of death [RR (HD:PD)].

RESULTS

Of the 398,940 patients studied, 11.6% used PD as initial therapy, 45% had diabetes mellitus (DM), 51% were 65 years or older, and 55% had at least one comorbidity. Among the 178,693 (45%) patients with no baseline comorbidity, adjusted mortality rates in nondiabetic (non-DM) patients were significantly higher on HD than on PD [age 18-44: RR (95% CI) = 1.24 (1.07, 1.44); age 45-64: RR = 1.13 (1.02, 1.25); age 65+: RR = 1.13 (1.05, 1.21)]. Among diabetic (DM) patients with no comorbidity, HD was associated with a higher risk of death among younger patients [age 18-44: RR = 1.22(1.05, 1.42)] and a lower risk of death among older patients [age 45-64: RR = 0.92 (0.85, 1.00); age 65+: RR = 0.86 (0.79, 0.93)]. Within the group of 220,247 (55%) patients with baseline comorbidity, adjusted mortality rates were not different between HD and PD among non-DM patients [age 18-44: RR = 1.19 (0.94, 1.50); age 45-64: RR = 1.01 (0.92, 1.11); age 65+: RR = 0.96 (0.91, 1.01)] and younger DM patients [age 18-44: RR = 1.10 (0.92, 1.32)], but were lower with HD among older DM patients with baseline comorbidity [age 45-64: RR = 0.82 (0.77, 0.87); age 65+: RR = 0.80 (0.76, 0.85)].

CONCLUSION

Valid mortality comparisons between HD and PD require patient stratification according to major risk factors known to interact with treatment modality. Survival differences between HD and PD are not constant, but vary substantially according to the underlying cause of ESRD, age, and level of baseline comorbidity. These results may help identify technical advances that will improve outcomes of patients on dialysis.

Body size and outcomes on peritoneal dialysis in the United States

BACKGROUND

Being overweight is often cited as a relative contraindication to peritoneal dialysis. Our primary objective was to determine whether actual mortality rates support this opinion.

METHODS

Retrospective cohort study of United States Medicare patients initiating dialysis between 1995 and 2000 (N = 418,021; 11% peritoneal dialysis).

RESULTS

Seven percent were underweight [body mass index (BMI) < 18.5 kg/m2], 27% were overweight (BMI 25.0 to 29.9 kg/m2), and 23% were obese (BMI> 29.9 kg/m2) at dialysis initiation. Compared to those with normal BMI, the adjusted odds of initiating peritoneal dialysis were 0.70 (P < 0.05) in underweight, 1.12 (P < 0.05) in overweight, and 0.87 (P < 0.05) in obese subjects. Among peritoneal dialysis patients, adjusted mortality hazard ratios in the first, second, and third year were 1.45 (P < 0.05), 1.28 (P < 0.05), and 1.17 for the underweight, respectively; 0.84 (P < 0.05), 0.89 (P < 0.05), and 0.98 for the overweight, respectively; and 0.89 (P < 0.05), 0.99, and 1.00 for the obese, respectively. Apart from higher third-year mortality in the obese, associations were similar after censoring at a switch to hemodialysis. For transplantation, the corresponding results were 0.76 (P < 0.05), 0.90 (P < 0.05), and 0.88 for the underweight, respectively; 0.95, 1.06, and 0.93 for the overweight, respectively; and 0.62 (P < 0.05), 0.68, and 0.71 for the obese, respectively. For switching to hemodialysis, hazards ratios were 0.92, 0.97, and 0.80 for the underweight, respectively; 1.07, 1.11 (P < 0.05), and 1.03 for the overweight, respectively; and 1.28 (P < 0.05), 1.29 (P < 0.05), and 1.36 (P < 0.05) for the obese, respectively.

CONCLUSION

Although less likely to initiate peritoneal dialysis, overweight and obese peritoneal dialysis patients have longer survival than those with lower BMI, not adequately explained by lower transplantation and technique survival rates.

Body size and outcomes on peritoneal dialysis in the United States

BACKGROUND

Being overweight is often cited as a relative contraindication to peritoneal dialysis. Our primary objective was to determine whether actual mortality rates support this opinion.

METHODS

Retrospective cohort study of United States Medicare patients initiating dialysis between 1995 and 2000 (N = 418,021; 11% peritoneal dialysis).

RESULTS

Seven percent were underweight [body mass index (BMI) < 18.5 kg/m2], 27% were overweight (BMI 25.0 to 29.9 kg/m2), and 23% were obese (BMI> 29.9 kg/m2) at dialysis initiation. Compared to those with normal BMI, the adjusted odds of initiating peritoneal dialysis were 0.70 (P < 0.05) in underweight, 1.12 (P < 0.05) in overweight, and 0.87 (P < 0.05) in obese subjects. Among peritoneal dialysis patients, adjusted mortality hazard ratios in the first, second, and third year were 1.45 (P < 0.05), 1.28 (P < 0.05), and 1.17 for the underweight, respectively; 0.84 (P < 0.05), 0.89 (P < 0.05), and 0.98 for the overweight, respectively; and 0.89 (P < 0.05), 0.99, and 1.00 for the obese, respectively. Apart from higher third-year mortality in the obese, associations were similar after censoring at a switch to hemodialysis. For transplantation, the corresponding results were 0.76 (P < 0.05), 0.90 (P < 0.05), and 0.88 for the underweight, respectively; 0.95, 1.06, and 0.93 for the overweight, respectively; and 0.62 (P < 0.05), 0.68, and 0.71 for the obese, respectively. For switching to hemodialysis, hazards ratios were 0.92, 0.97, and 0.80 for the underweight, respectively; 1.07, 1.11 (P < 0.05), and 1.03 for the overweight, respectively; and 1.28 (P < 0.05), 1.29 (P < 0.05), and 1.36 (P < 0.05) for the obese, respectively.

CONCLUSION

Although less likely to initiate peritoneal dialysis, overweight and obese peritoneal dialysis patients have longer survival than those with lower BMI, not adequately explained by lower transplantation and technique survival rates.

Hemoglobin levels and erythropoietin doses in hemodialysis and peritoneal dialysis patients in the United States

Erythropoietic agents, a cornerstone of management, are a major component of the cost of renal replacement therapy. The objectives of this study were to compare (on a month-by-month basis) U.S. hemodialysis and peritoneal dialysis patients in terms of the proportion of patients receiving erythropoietin, erythropoietin doses, and hemoglobin levels after initiation of erythropoietin. Patients studied (hemodialysis, n = 121,970; peritoneal dialysis, n = 7129) began dialysis between 1995 and 2000, had Medicare as their primary payer, were 65 yr old or older at dialysis inception, had no erythropoietin claims before dialysis inception, and did not have a switch in dialysis modality in the first 6 mo of dialysis therapy. Total monthly erythropoietin doses and average monthly hemoglobin levels were calculated from Medicare claims. The proportion of patients who received erythropoietin plateaued at 3 mo in both groups: 25% in peritoneal dialysis patients and 80% in hemodialysis patients. However, monthly erythropoietin doses plateaued at 30,000 units in peritoneal dialysis patients and 60,000 units in hemodialysis patients, a disparity not explicable by differences in baseline characteristics. Among subjects who received erythropoietin, mean hemoglobin levels were similar at steady state in both populations and met the National Kidney Foundation Dialysis Outcomes Quality Initiative hemoglobin target level of 11 to 12 g/dl. Hemoglobin levels in U.S. hemodialysis and peritoneal populations are similar. However, erythropoietin doses are dramatically higher in hemodialysis patients.

Eating ability in head and neck cancer patients after treatment with chemoradiation: A 12-month follow-up study accounting for dropout

BACKGROUND

Head and neck cancer patients treated with chemoradiation have difficulty eating a normal diet. This study was designed to characterize eating ability over 12 months after chemoradiation treatment. Analyses take patient dropout into account.

METHODS

Two hundred fifty-five patients with head and neck cancer treated with chemoradiation were followed for 12 months. Eating ability was analyzed using generalized linear model methods that accounted for non-ignorable dropout.

RESULTS

Eating ability was compromised immediately after treatment and improved over 12 months to near pretreatment levels. Ability to eat at most 50% of the diet orally did not return to baseline levels (p <.05). However, the percent of patients eating a normal diet did return to baseline levels. Accounting for dropout modified the results, but the pattern of significance was similar.

CONCLUSIONS

Treatment of head and neck cancer with chemoradiation has a significant effect on eating ability, which improves after 12 months after treatment.

The effect of technique failure on outcome in black patients on continuous ambulatory peritoneal dialysis

BACKGROUND

We previously reported that, while black patients have a better patient survival than white patients on peritoneal dialysis (PD), they also have a significantly higher technique failure rate (39% vs 8%, p < 0.0001). The purpose of this study was to determine the effect of technique failure/transfer to hemodialysis (HD) on patient survival in black PD patients.

METHODS

We retrospectively evaluated 137 incident black patients entering our PD program from January 1987 to December 1997. During the course of follow-up, 82 (60%) patients remained on PD (PD group) while 55 (40%) patients were permanently transferred to HD (PD-HD group). The primary outcome measured was patient survival.

RESULTS

Average age was 49 +/- 15 years, 42% were male, and 40% had diabetes mellitus. At baseline, serum creatinine was 10.8 +/- 5.4 mg/dL, serum albumin 3.4 +/- 0.7 g/dL, body mass index 27.3 +/- 6.5 kg/m2, peritoneal transport status was high in 18% and high-average in 61%, and residual glomerular filtration rate was 3.4 +/- 3.5 mL/minute. There were no significant differences in clinical features, nutritional status, peritoneal transport, residual renal function, or dialysis adequacy at baseline between the PD group and PD-HD group. While a greater proportion of patients transferring to HD had cardiac disease (53% vs 32%, p < 0.05), there were no other significant differences in 15 comorbid conditions assessed at baseline. The primary reason for transfer was peritonitis (64%) and the overall peritonitis rate in the PD-HD group was significantly higher than in the PD group (2.21 vs 1.17 episodes/patient-year, p < 0.0001). Overall follow-up was 34 +/- 25 months for PD group and 44 +/- 26 months for PD-HD group (p < 0.01), with a mean time on PD prior to transfer to HD of 22 +/- 18 months. During the course of follow-up, there were no significant differences between the two groups in the number of patients transplanted or deaths. Patient survival at 1, 2, and 5 years was 91%, 80%, and 57% for PD group and 96%, 92%, and 55% for PD-HD group [p = not significant (NS)]. A risk-adjusted time-dependent Cox regression analysis resulted in an adjusted relative risk of death that was not significantly different for those who transferred from PD to HD versus those who remained on PD (relative risk 1.49; 95% confidence interval 0.77-2.89; p = NS).

CONCLUSIONS

In black patients on PD, transfer to HD is not associated with any significant difference in patient survival compared to patients remaining on PD. While a high rate of peritonitis predisposes to technique failure, we found no features at baseline predictive of patients at greatest risk to fail PD. Since technique failure does not portend a poorer prognosis, PD remains a viable option for black patients entering an end-stage renal disease program.

Validation of PD Adequest 2.0 for pediatric dialysis patients

Kinetic modeling has proven to be a valuable tool for peritoneal dialysis (PD) prescription in adult PD patients. The clinical application of this procedure has rarely been studied in children. We therefore evaluated the PD Adequest 2.0 for Windows program (Baxter Healthcare Co., Deerfield, IL) as a prescription aid for the management of pediatric PD patients by comparing the measured and predicted PD clearances, total drain volumes, and net ultrafiltration in 34 children (15 males) (mean age 10.9 +/- 6.0 years) receiving long-term PD. In each case, a 4-h peritoneal equilibration test was conducted with a standardized test exchange volume of 1,100 ml/m2 BSA. A total of 43 24-h dialysate (plus urine in 12) collections were analyzed. The levels of agreement between measured and predicted values for weekly peritoneal and total urea Kt/V, weekly peritoneal and total creatinine clearance, daily drain volume, net ultrafiltration and daily peritoneal urea and creatinine mass removal were assessed with correlation coefficients (re) and Bland-Altman limits of agreement. The study revealed that there is a basic level of agreement between measured and modeled values for solute removal and total drain volume, with correlation coefficients ranging from 0.75 to 0.98. In contrast, the rc for net ultrafiltration was only 0.34. The majority (75%) of patients had modeled urea and creatinine clearances that were within 20% of their measured values. These data suggest that the PD Adequest 2.0 for Windows program can predict urea and creatinine clearances with reasonable accuracy in pediatric PD patients, making it a valuable resource in prescription management.

Patient survival among incident peritoneal dialysis and hemodialysis patients in an urban setting

We retrospectively evaluated 432 patients (336 black; 78%; and 96 white; 22%) incident to our peritoneal dialysis (PD; 195 patients; 45%) and hemodialysis (HD; 237 patients; 55%) programs from January 1987 to December 1997 who survived their first 90 days of dialysis therapy. Black patients comprised 70% of the PD and 84% of the HD patients (P: < 0.01). PD patients were more often men and younger than HD patients and less often had diabetes (40% versus 56% of HD patients; P: < 0.01) and cardiac disease (44% versus 58% of HD patients; P: < 0.01) than HD patients. Adjusting for baseline clinical and comorbid features, patient survival was determined by Cox regression analysis. Survival was better on PD therapy overall (relative risk [RR] for PD versus HD, 0.80; 1-, 2-, and 5-year survival rates, 90%, 77%, and 43% on PD versus 88%, 72%, and 35% on HD, respectively; P: = 0.21) and among black patients (RR for PD versus HD, 0.69; 1-, 2-, and 5-year survival rates, 92%, 80%, and 52% on PD versus 88%, 74%, and 40% on HD, respectively; P: = 0.09), but these were not statistically significant. The RR for PD versus HD was 1.08 for white patients (1-, 2-, and 5-year survival rates, 82%, 61%, and 23% for PD versus 82%, 62%, and 24% for HD; P: = 0.79). Significant predictors of mortality were race (RR for whites versus blacks, 1.51), age (RR, 1.03), cardiac disease (RR, 1.57), baseline albumin level (RR, 0.60), baseline serum creatinine level (RR, 0.91), baseline blood urea nitrogen level (RR, 1.01), and baseline weight (RR, 0.98). In conclusion, patient survival on dialysis therapy is significantly better for black patients and for patients entering dialysis with signs of adequate nutrition (increased weight and creatinine and albumin levels) and without evidence of cardiac disease. In an urban dialysis program, we find that adjusted patient survival on PD equals or is better than that on HD therapy, particularly among black patients, making PD a viable alternative to HD in our patient population.

Correlation between peritoneal equilibration test and dialysis adequacy and transport test, for peritoneal transport type characterization. Mexican Nephrology Collaborative Study Group

OBJECTIVE

The aim of this study was to analyze the correlation between the peritoneal equilibration test (PET) and the dialysis adequacy and transport test (DATT) for peritoneal transport type characterization, and the degree of patients' acceptance for each test.

DESIGN

Cross-sectional, observational multicenter study.

SETTING

Five referral (tertiary) dialysis centers of institutional practice.

PATIENTS

The study included 107 adult continuous ambulatory peritoneal dialysis (CAPD) patients with a prescription of four exchanges of 2 L per day, irrespective of age, gender, cause of end-stage renal disease, time on dialysis, nutritional status, or residual renal function. Patients on immunosuppressive therapy and those with cancer, hepatitis B, or HIV, and those having a peritonitis episode within the previous 30 days, or three or more episodes during the previous 12 months, were excluded.

MAIN MEASURES

Peritoneal transport type as classified by creatinine and urea dialysis-to-plasma (D/P) ratios by PET and DATT.

RESULTS

Correlation coefficients between D/P ratios for creatinine and urea, obtained for the PET and the DATT, were 0.73 for D/P creatinine and 0.96 for D/P urea. Patients were classified into high, high-average, low-average, and low transport categories according to the mean and standard deviation of D/P creatinine values obtained from the PET at 4 hours. These values showed excellent concordance with those generated from the DATT data (alpha = 0.82, 95% confidence interval 0.67 - 0.93). Nineteen percent of patients showed discordance in their category when classified according to the PET versus the DATT. Patients' acceptance was better for the DATT than for the PET, as evaluated with a questionnaire.

CONCLUSION

The DATT is an easy, inexpensive, and reliable test to assess peritoneal transport type, and it also provides information about peritoneal clearance of solutes and ultrafiltration. The DATT has better patient acceptance than the PET. Since the DATT has only been validated for patients on a fixed CAPD daily schedule of 4 x 2 L, the results should be confined only to patients receiving such a prescription.