Applying sigma metrics to assess quality control processes in the transfusion transmissible infection screening laboratory of a blood center

In the field of healthcare, quality and efficiency are of paramount importance to ensure the provision of safe and reliable diagnostic services. Blood screening laboratories play a critical role in detecting and preventing the spread of infectious diseases, ensuring the safety of blood transfusions, and supporting medical diagnoses. To enhance the quality of processes in such laboratories, the Six Sigma methodology has gained significant recognition for its ability to systematically identify and minimize variations, thereby improving overall efficiency and reducing errors. This retrospective study aims to explore the application of Six Sigma metrics in the context of blood screening laboratories, providing an in-depth analysis of its implementation, benefits, and challenges. The performance of three serology assays, i.e., anti-HCV, HIV Ag/Ab combo, and HBsAg, using internal quality control (IQC) daily data extracted from six Alinity i instruments (Abbott GmbH, Germany), from February to April 2023, was evaluated. Mean, standard deviation (SD), and coefficient of variation (CV%) was calculated for positive controls. Bias was calculated using peer group data. Sigma metrics were calculated using allowable total error (TEa %) based on difference between the observed mean of the positive control and the s/co cut-off of assay. The observed CV% for positive controls was ≤10%. The TEa% ranged from 66% to 79% for the analytes using the observed mean. All the assays showed Six Sigma performance (σ>6) with and without bias. The study observed that the serology assays showed very high sigma values (σ>6) and thus, simplified statistical quality control (SQC) design based on Westgard Sigma rules could be implemented without compromising blood safety.