PROTEIN CATABOLIC RATE IN PATIENTS ON CONTINUOUS PERITONEAL-DIALYSIS - A MULTIVARIATE PREDICTIVE MODEL

Protein catabolic rate (PCR) and PCR normalized to standard weight (PC RN) are important indices of nutrition in patients on continuous perit oneal dialysis. The purpose of this study was to test whether urea cle arance is among the predictors of PCR and PCRN in a multivariate analy sis. Stepwise logistic regression was used to develop separate models for low PCR and low PCRN on a set of 143 urea kinetic studies in 92 pa tients on continuous peritoneal dialysis. The regression models were t ested on an independent sample of 189 urea kinetic studies in 102 pati ents on continuous peritoneal dialysis by deriving the area under a re ceiver operating characteristic curve. In the derivation set, low seru m urea, high serum creatinine, low urine and dialysate drain volumes, and low body surface area were identified as predictors of PCR less th an or equal to 50 g daily. The area under the receiver operating chara cteristic curve in the validation set was 0.930 (95% confidence interv al: 0.915-0.945). Low serum urea, male gender, high body mass index an d low urea fractional clearance (KT/V) were predictors of PCRN less th an or equal to 0.80 g/kg daily. The receiver operating characteristic area for this model was 0.948 (95% confidence interval: 0.926-0.970). Logistic regression analysis was repeated twice after adding urea nitr ogen excretion normalized to standard weight (UNEN) as a candidate var iable. This process identified low UNEN, male gender, and obesity as t he predictors of low PCRN, and low UNEN, male gender, low urine volume , low drain volume normalized by body water, and high serum albumin as predictors of low KT/V urea. The authors conclude that PCR and PCRN c an be predicted by models that incorporate serum azotemic indices, bod y size and composition, and direct or indirect measurements of urea cl earance. Small body size and lean body composition predict low PCR but high PCRN values. Both PCRN and KT/V urea are predicted by UNEN. Mult ivariate analysis cannot, therefore, rule out the hypothesis that PCRN and KT/V are linked mathematically.