Peritoneal function and adequacy calculations: current programs versus PD Adequest 2.0.
OBJECTIVE: Our current programs (CPs) were compared to PD Adequest 2.0 (PD-A) for calculations of peritoneal membrane transport and dialysis adequacy. DESIGN: Thirty peritoneal equilibration tests (PETs) and 24-hour balances (24hBs) were conducted and calculated using our CPs and PD-A. PATIENTS AND METHODS: Thirty hospital-controlled peritoneal dialysis (PD) patients were studied. The inclusion of correction factors (for glucose or plasmatic water) and of residual volume, and the use of 3 or 6 peritoneal samples were analyzed to discover the differences between programs. The main outcome measures were peritoneal permeability and adequacy parameters, evaluated by Student t-test (mean and paired comparisons) and linear regression for correlation. RESULTS: No significant differences were found in D/P values for small solutes. At the first step, mass transfer area coefficient (MTAC) urea and MTAC creatinine were significantly higher in DP-A than in CP, but MTAC glucose did not differ. The causes of differences were: (1) inclusion of a correction factor for aqueous plasmatic concentration of small solutes in CP; (2) lack of Inclusion of residual volume in peritoneal volumes in CP; and (3) use of 6 peritoneal samples in CP versus 3 in PD-A. At the second step, when the input data were made equivalent for both programs, the differences disappeared for MTAC urea, creatinine, and glucose (mean comparison), but creatinine and glucose remained different by paired comparison. Similar results were obtained when a correction for plasmatic aqueous concentration was applied to the data in both programs [MTAC urea: 22.60 +/- 4.27 ml/min (CP) vs 22.43 +/- 4.61 mL/min (PD-A), nonsignificant, r= 0.97; MTAC creatinine: 9.76 +/- 3.83 mL/min (CP) vs 10.61 +/- 3.07 mL/min (PD-A), nonsignificant, r = 0.98; MTAC glucose: 13.30 +/- 3.12 mL/min (CP) vs 11.87 +/- 3.41 m/min (PD-A), nonsignificant, r= 0.92]. Creatinine and glucose were different by paired t-test. No significant differences were found in Kt/V and urea generation rate. Weekly creatinine clearance [WCCr: 70.71 +/- 16.71 L (CP) versus 79.33 +/- 18.73 L (PD-A), p < 0.001] and creatinine generation rate [CrGR: 0.56 +/- 0.18 mg/min (CP) versus 0.61 +/- 0.19 mg/min (PD-A), p < 0.001) were significantly higher in PD-A than In CP owing to the lack of creatinine correction according to glucose concentration In the PD-A adequacy program. Finally, normalized protein nitrogen appearance according to Bergström [1.09 +/- 0.20 g/kg/d (CP) versus 1.03 +/- 0.21 g/kg/d (PD-A), p = 0.01] was different owing to the different algorithms and normalization method: standardized body weight in CP and actual body weight in PD-A. CONCLUSIONS: Provided that equivalent data are used, PD-A and CP yield similar results. The PD-A program needs external correction of data input: (1) for plasmatic water concentration in MTAC calculations, and (2) for peritoneal glucose interference with creatinine analysis (Jaffé method) In WCCr and CrGR calculations; otherwise, It may give falsely optimistic results.