Online Urea Concentration Estimation from Spent Dialysate Using Optical Sensor

The aim of this study was to estimate urea concentration on-line in the spent dialysate by a novel miniaturized optical sensor during hemodialysis and hemodiafiltration with different settings, and to compare the results with urea concentrations measured in laboratory. Ten end-stage kidney disease patients were enrolled for this study and the dialysate samples were collected, and signals were recorded with optical sensor during 5 midweek dialysis sessions with 5 different modalities for each patient. Using samples and optical signals from calibration set, the linear model was calculated to estimate urea concentration. For linear model the determination coefficient R-2, the systematic error as BIAS and the standard error (SE) were 0.876, 0.00 +/- 1.60 mM/L (calibration set) and 0.841, 0.01 +/- 1.68 mM/L (validation set), respectively. In summary, the novel miniaturized optical sensor enables on-line estimation of urea concentrations during dialysis sessions and accuracy outperforms the measurement accuracy of UV-absorbance based urea concentration method from a previous study.