Study On Allowable Imprecision,Allowable Bias And Allowable Total Error Of Routine Quantitative Tests In Clinical Laboratories

ObjectiveThere are 3 models of setting performance specifications that were defined in the Milan Conference.This study used 2 of them—setting performance specifications based on biological variation(BV)and setting performance specifications based on the state-of-the-art,as well as the data of External Quality Assessment(EQA)and Internal Quality Control(IQC),to discuss and recommend allowable imprecision(allowable CV),allowable bias and allowable total error(TEa)for 68 routine quantitative tests in clinical laboratories in China.MethodFor each research item,the EQA data from the beginning of EQA plan and the IQC data from the beginning of IQC plan were collected by the web-based EQA software.The Excel 2016,SPSS 19.0 and the analytical software developed together by National Center for Clinical Laboratories(NCCL)and Beijing Clinet Information Technology Limited Company(www.clinet.com.cn)were applied to analyze and calculate the 'percentage difference' of all lots in each year and P10(the 10th percentile)and P90(the 90th percentile)of 'percentage difference' of all laboratories in each lot by EQA data,as well as P so(the 80th percentile)of 'in-control coefficient of variation(CV)' of all lots in each year by IQC data for all items.For each item having BV data,'percentage difference' were respectively compared with three level TEa derived from BV,evaluation criteria in Chinese EQA and RCPAQAP,then the pass rates of 'percentage difference' were calculated for all lots in each year.By comparing the difference of the pass rates of 'percentage difference' among many years,the change of total error in the testing of each item would be reflected.In addition,for each item,if all lots in 2016 had the pass rates of 'percentage difference' more than 80%when compared with one TEa derived from BV,this TEa would satisfy the requirement to be the recommendatory TEa of this item.If many TEa derived from B V all satisfied the requirement,the most stringent(smallest)one would be the recommendatory TEa.Meanwhile,for each item having BV data,the 'in-control CV' were respectively compared with three level allowable CV derived from BV,1/3TEa and 1/4TEa(TEa is the evaluation criterion of each item in Chinese EQA),then the pass rates of 'in-control CV'were calculated for all lots in each year.By comparing the difference of the pass rates of'n-control CVi' among many years,the change of imprecision in the testing of each item would be reflected.In addition,for each item,if all lots in 2016 had the pass rates of 'in-control CV' more than 80%when compared with one allowable CV derived from BV,this allowable CV would satisfy the requirement to be the recommendatory allowable CV of this item.If many allowable CV derived from BV all satisfied the requirement,the most stringent(smallest)one would be the recommendatory allowable CV.For items not having BV data or items which could not use performance specifications derived from BV as recommendatory criteria,the performance specifications based on the state-of-the-art would be used as their recommendatory TEa and allowable CV.For each item,after acquiring the recommendatory TEa and allowable CV,the formula |bias|?TEa-zxCV(the value of z is always 1.65)could be applied to obtain the recommendatory allowable bias.ResultThe results of EQA data of all items showed that 40 items had pass rates of percentage difference more than 80%for all lots in 2016 in the comparison to one or several TEa derived from BV,therefore they could use the TEa derived from BV as their recommendatory TEa,but other 28 items used the TEa based on the state-of-the-art as their recommendatory TEa.The comparison between recommendatory TEa and the evaluation criterion in Chinese EQA for each item suggested that 2,51 and 7 items had recommendatory TEa respectively equal to,less than and larger than their evaluation criteria in Chinese EQA.The results of IQC data of all items indicated that 25 items had pass rate of CV more than 80%for all lots in 2016 in comparison to one or several allowable CV derived from BV,therefore they could use the allowable CV derived from BV as their recommendatory allowable CV,other 42 items exploited the allowable CV based on state-of-the-art as their recommendatory allowable CV,and the remained 1 item did not have the recommendatory allowable CV because its imprecision was larger than total error.Among all items,items which had allowable bias and not had allowable bias are both 34.ConclusionThis was the first study on allowable CV,allowable bias and TEa for such many(68)routine quantitative tests in China.In this study,the performance level which could be achieved for 68 items were reflected and the allowable CV,allowable bias and TEa conformed to the Chinese current situation for all items were recommended.