Measured-to-predicted creatinine generation ratio increases with time and decline in residual renal function in continuous ambulatory peritoneal dialysis

The expression of measured-to-predicted creatinine generation ratio (MIP) h as been proposed as an index of compliance in continuous ambulatory periton eal dialysis (CAPD) patients. Although M/P may not be sensitive enough for cross-sectional study, serial monitoring has been suggested to identify non compliance. We attempted to evaluate serial changes of M/P from a nonselect ed group of CAPD patients, Sixty-three patients, all followed up for 2 year s, were reviewed retrospectively. Their MIP ratios at years 0 and 2 were co mputed and compared, Baseline MIP had a normal distribution with a mean of 0.96 +/- 0.26. There was significant correlation between baseline MIP and r esidual glomerular filtration rate (GFR; r = -0.81; P < 0.0001). There were weak correlations between M/P and duration of dialysis (r = 0.52; P < 0.00 01), body weight (r = -0.52; P < 0.0001), KW (r = 0.31; P < 0.02), weekly c reatinine clearance normalized to body surface area (r = 0.53; P < 0.0001), and serum albumin level (r = -0.28; P < 0.05), After 2 years, M/P increase d in 56 of 63 patients (88.9%). Average M/P increased from 0.96 +/- 0.26 to 1.31 +/- 0.27 (P < 0.0001). Multivariant analysis showed MIP at year 0, wh ich was largely determined by residual GFR, was the only independent factor affecting increase in M/P from year 0 to year 2. The general trend of incr easing M/P was still present when only anuric patients were analyzed, altho ugh that was not statistically significant (1.21 +/- 0.14 to 1.32 +/- 0.24; P = 0.12). The finding of increasing M/P with time in CARD patients, parti cularly those with significant residual renal function, suggests MIP may no t be a reliable indicator of noncompliance, even for serial follow-up of th e same patient. Better methods for assessment of compliance in CAPD patient s are required. (C) 1999 by the National Kidney Foundation, Inc.