Mass transfer coefficient: comparison between methods

The mass transfer area coefficient (MTC) is the best parameter for solute transport evaluation in continuous ambulatory peritoneal dialysis (CAPD) patients. We compared three simplified MTC methods (calculated according Garred, Krediet, or Lindholm) and the peritoneal equilibration test (PET) (Twardowski) to complex MTC (MTCX) (Randerson and Farrell) for urea and creatinine, by means of 29 tests performed in 24 stable CAPD patients. There were no significant differences (paired t-test) between MTCX and each of the simplified MTC, except for creatinine MTC calculated by Krediet's method, which was significantly different (MTCX: 9.36 +/- 4.32, K-MTC: 10.48 +/- 4.55, p < 0.05). Likewise, there was an acceptable correlation between complex MTC and each of the simplified methods including the PET. However, a more detailed study of the MTC's categorizations shows poor agreement with complex MTC categorization. Better results are obtained by PET categorization, which reaches good likelihood ratios either for positive or negative events. We conclude that simplified MTC or the dialysate/plasma ratio at 240 minutes for urea and creatinine has an acceptable correlation with complex MTC and can be useful in clinical practice. There is poor agreement between solute transport categorizations of simplified MTC and complex MTC. There is a better coincidence between the PET (D/P at 240 minutes) and complex MTC categorizations.