Creatinine kinetic modelling: a simple and reliable tool for the assessment of protein nutritional status in haemodialysis patients

While the mathematical modelling of urea kinetics is in wideuse for evaluating treatment adequacy and protein nutritionin dialysis patients, the kinetics of creatinine generationin dialysis patients has been relatively unexplored. In thisstudy creatinine kinetic modelling as a clinical tool was investigatedin a group of 90 patients treated by haemodialysis (n=20), haemodiafiltration(60), haemofiltration (7), or biofiltration (3) over a 6–36-monthperiod. A single pool model of creatinine kinetics was employedto obtain monthly values of creatinine distribution space andcreatinine appearance rate. Extrarenal creatinine degradationrate, estimated using a clearance of 0.038 l/kg/24 h as suggestedby Mitch and co-workers, was added to creatinine appearancerate in urine and dialysate to calculate a corrected creatinineindex (CI). Extrarenal degradation accounted for 12 ±2% of CI. CI was higher in males (22.4 ± 4.5 mg/kg/24h) than females (19.8 ± 4.8) and decreased with age,falling off more sharply for the female group (CI=29.9–0.185.age,R=0.72) than the males (CI=24.1–0.030.age, R=0.31). CIwas found to correlate strongly with protein catabolic ratedetermined by urea kinetic modelling (CI=8.84+10.91.PCR). Lowor reduced CI was associated in this study group with severemalnutrition status and high mortality rate. CI is suggestedas a strong predictor of patient morbidity and mortality.