Objective To discuss the comparability of blood urea nitrogen (BUN),creatinine (Cr),uric acid (UA) results and provide basis for result concordance in different biochemical systems.Methods The within-run precision and the between-day precision for the median and high values of quality control materials were tested in Beckman LX-20 and Hitachi 7600 chemistry analyzer respectively,and the evaluation criteria were according to the precision requirement of manufacturer and our laboratory.According to American Clinical and Laboratory Standards Institute (CLSI) document EP9-A2,serum BUN,Cr,UA from 40 patients were detected by Hitachi 7600 chemistry analyzer as experimental method and by Beckman LX-20 chemistry analyzer as comparative method.The relative bias ( SE％) between experimental method and comparative method was calculated and the concordance of biochemical analysis system was determined according to EQA requirements and acceptable performance criteria Results The between-run and between-day precision coefficients of variation for BUN,Cr and UA in two biochemical analysis systems were lower than the precision requirement of manufacturer and our laboratory.In Hitachi 7600 chemistry analyzer,the SE％ for BUN at three levels of medical decision were 9.4％,2.0％ and 0.8％,the SE％ for Cr were 7.3％,3.8％ and 2.8％,the SE％ for UA were 7.9％,1.7％ and 1.2％.Two biochemical analysis systems were not comparable in BUN analysis because SE％ of serum BUN levels detected by Hitachi 7600 at low medical decision level exceeded the specified range.The remaining items between two biochemical analysis systems were concordant.Conclusion While the same test is detected by more than two systems in one laboratory,it is necessary to do method comparison and bias evaluation for concordance in order to ensure the comparability among test results.