Developing analytical parameters and evaluation of thermo fisher urinary creatinine enzymatic method to implement in open system chemistry analyzers

Creatinine assay is used mainly to monitor kidney function and for sample validity when testing for drugs of abuse. Creatinine alkaline picrate method based on Jaffe’s reaction calls for extra cleaning procedures to minimize interference from picric acid and sodium hydroxide. Thermo Fisher enzymatic method is more sensitive and specific when compared to alkaline picrate method, but there were no available analytical parameters to setup this enzymatic method on open chemistry analyses platform such as Beckman-Coulter AU5800 analyser. Specific analytical parameters were developed and the assay performance is evaluated against the alkaline picrate method.  We successfully set up analytical parameters on Beckman-Coulter AU5800, as an example of open system analyser, and evaluated its performance against Thermo Fisher Jaffe’s reaction method. The weighted Deming regression analysis for 408 samples showed a good correlation at a 95% confidence interval. Slope is 1.065 to 1.091, Y-intercept when X=0.0 is -0.9377 to -0.5443 and correlation coefficient (r) is 0.993. The alkaline picrate method Mean and SD for tested samples are 13.2877 and 7.414 respectively and for the enzymatic method are 13.5823 and 7.987 respectively. Many interferences from drugs and other substances are eliminated when using the enzymatic method and the stability of other reagents on-board improved because the reagents used in the enzymatic method are less invasive.