Application value of 6 sigma quality management theory in clinical tumor marker testing

Ding Yi; Pu Xiaohong; Zhang Song; Wan Chuandan; Huang Shaozhi

doi:10.3969/j.issn.1674-7151.2025.02.005

Abstract：Objective To evaluate the quality control(QC)performance of tumor marker testing using six sigma(6σ)management theory and guide continuous improvement of laboratory quality management in clinical biochemistry laboratories.Methods The internal QC data of 9 projects[carcinoembryonic antigen(CEA),alpha-fetoprotein(AFP),carbohydrate antigen 153(CA153),carbohydrate antigen 199(CA199),carbohydrate antigen 125(CA125),total prostate-specific antigen(tPSA),free prostate-specific antigen(fPSA),cytokeratin 19 fragment(CYFRA21-1),and ferritin(Fer)]in clinical biochemical laboratories were used to estimate the imprecision estimation.The internal QC included two levels(low level 1 and medium level 2)for all projects.National external quality assessment(EQA)data of tumor markers in 2022 were used as the source of bias calculation.The σ values of 9 tumor markers were calculated using National Center for Clinical Laboratory Medicine EQA standards and biologically derived variation-based criteria.Combined with Westgard Sigma rules,standardized sigma performance verification charts were generated to evaluate analytical performance,design personalized QC strategies,and identify improvement directions.For projects with σ<6,quality goal index(QGI)was calculated,the reasons for poor performance were identified and the direction for quality improvement was clarified.Results tPSA and fPSA had σ<3(poor performance),AFP,CA153,CYFRA21-1 and Fer fell into 3≤σ<4 range(marginal performance),CA125 achieved 4≤σ<5(good performance),and CEA and CA199 reached 5≤σ<6(excellent performance).No projects achieved σ≥6.The average σ value was 3.82.CEA and CYFRA21-1 had QGI values of 0.8-1.2,requiring improvements in accuracy and precision.Performance validation chart for tumor markers was drawn and combined with Westgard rules,recommended QC plans for each project were derived.CYFRA21-1 and Fer could adopt 13S,22S,R4S,41S(N=4,R=1 or N=2,R=2)rules to enhance precision management,and marginal projects(AFP and CA153)were advised to use 13S,22S,R4S,41S,8x-(N=4,R=2 or N=2,R=4)rules.Conclusion 6σ quality management theory is an advanced quality management tool,which could objectively evaluate the performance level of tumor marker testing items,guide laboratory to design personalized QC rules for the items and take various quality improvement measures,which could help to continuously monitor and improve the quality level of testing.