Application of different allowed total error in the performance evaluation of tumor marker determination and selecting quality control rule

Objective To study the application of different allowed total error(TEa) in the performance evaluation of tumor marker determination,and select and optimize the quality control rules according to 6 sigma(6σ).Methods The σ levels of alpha-fetoprotein(AFP),carcino-embryonic antigen(CEA),prostate specific antigen(PSA),carbohydrate antigen(CA)199,CA125 and CA153 were calculated according to the formula: σ=(TEa-bias)/coefficient of variation(CV).The CV and bias were collected and calculated from intra quality control from June to December 2009 and the mean value of inter quality control,respectively.TEa was quoted from the Clinical Laboratory Improvement Amendments 88(CLIA′88),Rilibak(German guidelines for quality),the requirements of the Royal College of Pathologists of Australasia(RCPA) and biological variation data.Results The σ values of tumor markers such as AFP,CEA,PSA,CA199,CA125 and CA153 were from 0.71-9.82 in Roche E601 chemiluminescence analyzing system.The performance expressions were different with different TEa.The quality control rules should be chosen appropriately according to different levels.Conclusions Clinical laboratory can select different quality control rules in line with σ level calculated by different TEa in order to perform intra quality control economically and reasonably.