CORRECTION OF GLUCOSE-CONCENTRATION INTERFERENCE ON JAFFE KINETIC CREATININE ASSAY IN PERITONEAL-DIALYSIS

Overestimation of creatinine measurement using the Jaffe kinetic metho d in peritoneal dialysis solutions, due to glucose interference, has b een quantified and corrected through the elaboration of linear formula s obtained from 110 recovery and 301 biological tests. The added pure powdered creatinine and enzymatic method were considered as references after proven accuracy. Considering creatinine as well as glucose conc entration interference, we obtained correction formulas from multiple regression application, All the computed formulas gave satisfactory co rrections but different accuracy levels. The best model in biological samples was: Corrected CR = K(1)JaffeCr + K(2)Glucose (all values in m g/dl) where K-1 = 0.973 and K-2 = -0.00035 (Rsq = 0.987, F ratio 10,94 5, p = 0.00001). Applying formulas to biological samples there was a d rop in accuracy, possibly explained by the presence of numerous uniden tified substances in peritoneal dialysis biological samples that can a mplify scatter. Every laboratory can reduce the error of the Jaffe kin etic assay by calculating their own correction formula in relation to the method and instrument used, because Jaffe kinetic assay gives diff erent results with different kinetic windows. So, especially when appl ied to peritoneal dialysis fluid measurements, if a creatinine assay r eference method is not available, the correction formula can be applie d directly as given. Otherwise the method we have described can be fol lowed with a well-structured creatinine recovery fest to identify and quantify assay interferences.