title: Baseline Residual Kidney Function and Its Ensuing Rate of Decline Interact to Predict Mortality of Peritoneal Dialysis Patients.
abstract: BACKGROUND
  Baseline residual kidney function (RKF) and its rate of decline during follow-up are purported to be reliable outcome predictors of patients undergoing Peritoneal Dialysis (PD). The independent contribution of each of these factors has not been elucidated.
  
  
  METHODS
  We report a multicenter, longitudinal study of 493 patients incident on PD and satisfying two conditions: a glomerular filtration rate (GFR) ≥1 mL/minute and a daily diuresis ≥300 mL. The main variables were the GFR (mean of urea and creatinine clearances) at PD inception and the GFR rate of decline during follow-up. The main outcome variable was patient mortality. The secondary outcome variables were: PD technique failure and risk of peritoneal infection. The statistical analysis was based on a multivariate approach, placing an emphasis on the interactions between the two main study variables.
  
  
  RESULTS
  Baseline GFR and its rate of decline performed well as independent predictors of both patient mortality and risk of peritoneal infection. These two main study variables maintained a moderate correlation with each other (r2 = 0.12, p<0.0005), and interacted clearly, as predictors of patient mortality. A low baseline GFR followed by a fast decline portended the worst survival outcome (adjusted HR 3.84, 95%CI 1.81-8.14, p<0.0005)(Ref. baseline GFR above median plus rate of decline below median). In general, the rate of decline of RKF had a greater effect on mortality than baseline GFR, which had no detectable effect on survival when the decline of RKF was slow (HR 1.17, 95% CI 0.81-2.22, p = 0.22). Conversely, a relatively high GFR at the start of PD still carried a significant risk of mortality, when RKF declined rapidly (HR 1.89, 95% CI 1.05-3.72, p = 0.028).
  
  
  CONCLUSIONS
  The risk-benefit balance of an early versus late start of PD cannot be evaluated without taking into consideration the rate of decline of RKF. This circumstance may contribute to explain the controversial results observed at the time of evaluating the potential benefits of an early initiation of PD.
authors.affiliation: Division of Nephrology, University Hospital of A Coruña, A Coruña, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Pérez Fontán
authors.affiliation: Division of Nephrology, University Hospital Puerta Real, Cádiz, Spain.
authors.forename: César
authors.initials: C
authors.lastname: Remón Rodríguez
authors.affiliation: Division of Nephrology, University Hospital of A Coruña, A Coruña, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: da Cunha Naveira
authors.affiliation: Division of Nephrology, University Hospital Arnau de Vilanova, Lleida, Spain.
authors.forename: Mercè
authors.initials: M
authors.lastname: Borràs Sans
authors.affiliation: Division of Nephrology, University Hospital of Asturias, Oviedo, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Rodríguez Suárez
authors.affiliation: Division of Nephrology, University Hospital Puerta Real, Cádiz, Spain.
authors.forename: Pedro
authors.initials: P
authors.lastname: Quirós Ganga
authors.affiliation: Division of Nephrology, University Hospital of Asturias, Oviedo, Spain.
authors.forename: Emilio
authors.initials: E
authors.lastname: Sánchez Alvarez
authors.affiliation: Division of Nephrology, University Hospital of A Coruña, A Coruña, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Rodríguez-Carmona
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007668:Kidney / Q000473:pathology / Q000503:physiopathology*; D007677:Kidney Function Tests; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010530:Peritoneal Dialysis; D010538:Peritonitis / Q000401:mortality* / Q000473:pathology / Q000628:therapy*