Analytical reliability of clinical laboratories may be obtained by internal quality control,
external quality control by analyzing the data with statistical methods. In Six Sigma Methodology, which
is one of these methods, the analytical performance of the tests is determined by process sigma values.
In this study, we aimed to assess the analytical process performances of most frequently used tests in
our laboratory according to six sigma methodology.
Material and Methods: Internal quality control data between July- October 2014 were obtained from
the laboratory information system. Process sigma levels based on formula (% TEa - % Bias) / % CV)
were calculated for the analytes. The results were classified in 3 groups according to sigma level as low
≤4; acceptable between 4–6; good ≥6.
Results: Tests having a process sigma level of ≤ 4; in July: level 1; Glucose, Creatinine, level 2; Urea,
Glucose, Creatinine, Total Protein, in August: level 1; Alb, ALP, Urea, Glucose, Creatinine, Total Protein,
level 2; Alb, ALT, Urea, Glucose, Creatinine, Total Protein September: level 1; Urea, Glucose, Total
Protein, level 2; Glucose, Total Protein.
Conclusion: This study showed that tests with low process sigma levels in our laboratory can be
determined and these tests may ve evaluated as a whole with preanalytical and postanalytical
processes. Six sigma methodology may provide a detailed assessment of measurement processes with
problematic analytical process sigma levels and controlling the variables.