Abstract:

Objective To establish and validate the coupledenzyme equilibrium reference method as a reference method for urea detection and compare it with other 4 routine urea kits.
Methods The reference method was verified by testing the two levels of urea in SRM909b and participating in RELA-2009. The EP9-A2 protocol was used to compare the results in forty serum samples in 4 routine kits methods with coupled-enzyme equilibrium reference method.
Results The deviation of SRM909b level 1 was 2.19% and SRM 909b level 2 were 0.24% respectively through determining by the reference method. The results for RELA-2009 were within the accepted range. Comparing the confidence interval of the predicted bias with the definition acceptable error at the medical decision point Xc(Xc=9.64 mmol/L) for the 4 routine kits, the results were all within the range of defined acceptable error(4.5%) and the range of biological variation bias(5.5%).
Conclusion The coupled-enzyme equilibrium reference method for serum urea was established in our lab. The urea results measured with 4 routine kits were different from results with the reference method, but the deviation was acceptable, and it will not affect the detection results.

Key words: urea, reference method, coupled-enzyme equilibrium, spectrophotometry, ultraviolet, evaluation study