Assessing Creatinine Clearance from Modification of Diet in Renal Disease Study Equations in the ADEMEX Cohort

Abstract

SummaryBackground 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, & measurementsPost 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 Ͻ 12 ml/min per 1.73 m 2 . Although there was no association between survival and mCrCl, for every 1-ml/min per 1.73 m 2 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.

Serum creatinine level, a surrogate of muscle mass, predicts mortality in peritoneal dialysis patients

“…A recent post hoc analysis of data from PD patients enrolled in ADEMEX study demonstrated that every 1 mL/ min/1.73 m 2 increase in estimated GFR by the four-variable MDRD equation was associated with a 6% increase in risk of death, but there was no association between measured Cr clearance and survival. This study also demonstrated a negative association between estimated GFR and Cr appearance rates [32]. Our results also suggest that muscle mass plays a predominant role in the serum Cr-mortality association in PD patients, supporting findings from earlier studies.…”

“…In addition, some studies evaluating a survival benefit of early start of dialysis showed that a higher estimated GFR based on serum Cr level at dialysis initiation was associated with poorer survival, which could not be fully abolished by adjusting for known confounders such as age, sex, race, comorbidities, hemoglobin and serum albumin level [36][37][38]. This phenomenon is also likely to be caused by patients with a low muscle mass leading to a low plasma Cr and thus a high estimated GFR [32,39]. Our results showed that the association between higher serum Cr level with greater survival is still observed in a large PD cohort.…”

“…proxy of larger muscle mass) would relate to greater survival. In a recent study of PD patients, higher estimated GFR by the Modification of Diet in Renal Disease (MDRD) equation [30,31] was associated with increased mortality, but measured GFR was not related to mortality [32]. These data suggest that, in PD patients, serum Cr level may in fact be a surrogate of muscle mass, and that low muscle mass is associated with worse outcomes in this context.…”

Estimated glomerular filtration rate in peritoneal dialysis practice

“…As reported by the Modification of Diet in Renal Disease equations [4,5], more extensive and longterm studies will be needed to clarify eGFR, as proposed by JSN, as a new marker in the evaluation of PD dose and adequacy, because the simplicity of eGFR will be valuable in studies requiring huge sample sizes or the cooperation of multiple medical facilities.…”