Application of Six Sigma Model to Evaluate the Analytical Quality of Four HbA1c Analyzers.

BACKGROUND

The Six Sigma Model is a global quality management system applicable to the determination of glycated hemoglobin (HbA1c). In addition, this model can ensure the three characteristics influencing the patient risk: the correct performance of the analytical method with low inaccuracy and bias, the quality control strategy used by the laboratory, and the necessary quality of the analyte. The aim of this study is to use the Six Sigma Model for evaluating quality criteria in the determination of glycated hemoglobin HbA1c and its application to assess four different HbA1c analyzers.

METHODS

Four HbA1c analyzers were evaluated: HA-8180V®, D-100®, G8®, and Variant II Turbo®. For 20 consecutive days, two levels of quality control (high and low) provided by the manufacturers were measured in each of the instruments. Imprecision (CV), bias, and Sigma values (σ) were calculated with the data obtained and a method decision chart was developed considering a range of quality requirements (allowable total error, TEa).

RESULTS

For a TEa = 3%, HA-8180V = 1.54 σ, D-100 = 1.63 σ, G8 = 2.20 σ, and Variant II Turbo = -0.08 σ. For a TEa = 4%, HA-8180V = 2.34 σ, D-100 = 2.32 σ, G8 = 3.74 σ, and Variant II Turbo = 0.16 σ. For a TEa = 10%, HA8180V = 7.12 σ, D-100 = 6.46 σ, G8 = 13.0 σ, and Variant II Turbo = 1.56 σ.

CONCLUSIONS

Applying the Stockholm consensus and its subsequent Milan review to the results: the maximum level in quality requirements for HbA1c is an allowable total error (TEa) = 3%, G8 is located in region 2 σ (2.20), which is a poor result, and HA-8180V and D-100 are both in region 1 σ (1.54 and 1.63, respectively), which is an unacceptable analytical performance.