Six sigma is a quality management tool used to evaluate analytical process performance. We
evaluated the performance of biochemical and immunological tests on a Roche Cobas 8000 device in
our laboratory using sigma metrics.
Materials and Methods: Six-month (September 2018 to February 2019) data on internal quality
control (IQC) and external quality control (EQC) were extracted for each assay. The precision and bias
were calculated for IQC and EQC, respectively. The sigma values for each assay were calculated using
precision, bias, and total allowable error (TEa) ratios of CLIA 2019.
Results: Sigma values of ALB, GLU, Ca, CI, CREA, Na, K, TP, urea, and complement C3 were below 3.
ALT, AST, Amylase, P, GGT, HDL-C, CHOL, LDH, LDL-C, T-BIL, UIBC, UA, CRP, complement C4, IgA, and
IgM were between 3 and 6 sigma. Sigma values of CK, D-BIL, lipase, and IgG were greater than 6.
Conclusion: Because most sigma values were above 3, the analytical performances of assays in our
laboratory were acceptable. However, parameters with sigma values less than 3 should be strictly monitored.