Carbamylated Haemoglobin, Urea Kinetic Modelling and Adequacy of Dialysis in Haemodialysis Patients

Urea kinetic modelling (UKM) has increasingly been used for assessing adequacy of dialysis and protein nutritional status of dialysis patients. Using a precise HPLC method we developed, we measured carbamylated haemoglobin (CarHb) values in 20 stable twice-weekly dialysed patients and attempted to correlate their CarHb values with their UKM-derived indices. Based on these indices, 11 patients were found to have been adequately dialysed with sufficient protein intake, three patients were adequately dialysed but malnourished and six patients were under-dialysed. Estimated dietary protein intake correlated poorly with calculated daily protein catabolic rate in our patients. CarHb values were found to correlate strongly with the time-averaged urea concentrations, suggesting that CarHb might be a time-integrated urea-derived index. Those adequately dialysed patients have a mean (SD) CarHb value of 142 (29) μg CV/gHb against the underdialysed patients, 197 (30) μg CV/gHb (t-test, P=0.002). We suggest that a CarHb value 175 μg CV/gHb is undesirable.