A comparison of peritoneal equilibration tests performed 1 and 4 weeks after PD commencement.

Objective: The aim of this study was to prospectively evaluate the ability of a peritoneal equilibration test (PET) performed in the first week of peritoneal dialysis (PD) to predict subsequent transport status, as determined by a PET at 4 weeks and >1 year after PD commencement.

Design: Prospective observational study of an incident PD cohort at a single center.

Setting: Tertiary-care institutional dialysis center.

Participants: The study included 50 consecutive patients commencing PD at the Princess Alexandra Hospital between 25/2/2001 and 14/5/2003 (mean age 60.9 +/- 12.2 years, 54% male, 92% Caucasian, 38% diabetic). All patients were initially prescribed continuous ambulatory PD.

Main Measurements: Measurements performed during paired PETs included dialysate-to-plasma ratios of urea (D/P urea) and creatinine (D/P creatinine) at 4 hours, the ratio of dialysate glucose concentrations at 0 and 4 hours (D/D0 glucose), and drain volumes at 4 hours.

Results: When paired 1-week and 1-month PET data were analyzed, significant changes were observed in measured D/P urea (0.91 +/- 0.07 vs 0.94 +/- 0.07 respectively; p < 0.05), D/P creatinine (0.55 +/- 0.12 vs 0.66 +/- 0.11, p < 0.001), and D/D0 glucose (0.38 +/- 0.08 vs 0.36 +/- 0.10, p < 0.05). Using Bland-Altman analysis, the repeatability coefficients were 0.17, 0.20, and 0.13, respectively. Agreement between 1-week and 1-month PET measurements with respect to peritoneal transport category was moderate for D/D0 glucose (weighted kappa 0.52), but poor for D/P urea (0.30), D/P creatinine (0.35), and drain volumes (0.20). The PET measurements performed more than 1 year following PD commencement (n = 28) generally agreed closely with 1-month measurements, and poorly with 1-week measurements.

Conclusions: Peritoneal transport characteristics change significantly within the first month of PD. PETs carried out during this time should be considered preliminary and should be confirmed by a PET 4 weeks later. Nevertheless, performing an early D/D0 glucose measurement at 1 week predicted ultimate transport status sufficiently well to facilitate early clinical decision-making about optimal PD modality while patients were still receiving PD training. On the other hand, the widespread practice of using measured drain volumes in the first week to predict ultimate transport category is highly inaccurate and not recommended.