Creatinine is the best molecule to target adequacy of peritoneal dialysis.

The overall conclusion is that neither creatinine clearance nor urea clearance is the perfect index for predicting outcome in PD patients. In the absence of indices that are better validated and more convenient, creatinine and urea are what we have to use. They are best seen as two imperfect, but potentially complementary, measurements. On balance, creatinine clearance is the better of the two indices, in that it gives greater weight to residual renal function, and residual renal function is probably a stronger predictor of patient outcome than peritoneal clearance per se. However, creatinine clearance has a particular weakness in low transporters; values have to be interpreted with discretion in this group. Furthermore, both indices are flawed because of the manner in which they are conventionally normalized. Research into more appropriate methods of normalization, or into whether normalization is required at all, would be helpful. The complex relationship between these clearance indices, protein intake, and lean body mass also needs to be kept in mind. While this paper argues in favour of creatinine clearance as the better index, it still suggests that both indices be used, together with a large measure of clinical judgment.