An Excel Visual Basic for Application worksheet for automatic selection of a sigma statistical quality control procedure, facilitating quality management for laboratories

Abstract

Defining the proper statistical quality control (SQC) procedure and designing the quality control plan provide the analytical quality management (QM) that is essential in laboratory practice, ensuring that reported test results achieve the quality required for medical decisions. The Westgard sigma rules with run size, one of the popular quality control planning tools, is an effective tool for evaluating measurement performance and simplifying an appropriate selection of SQC. To achieve QM, the author established an Excel Visual Basic for Application (VBA) worksheet for automatic sigma scale calculation and automatic selection of SQC procedures. This file applied the Westgard sigma rules with run size concept, developed for a convenient multistage SQC design. In addition, there are more functions for monitoring QC results, documenting, and compiling the corrections utilized to improve QC design. Of 23 assays from our laboratory, only one-fifth of the tests (22%) achieved an optimal level of performance (≥ 6 sigma). Analytes with the highest sigma performance were triglyceride, high-density lipoprotein (HDL), low-density lipoprotein (LDL), magnesium (Mg) and creatine phosphokinase (CK). In contrast, one-third of the tests (35%) had a sigma scale of less than 4, requiring them to be solved, improved and have rigorous QC monitoring by primary following in the Data Analysis sheet. Thus, this Excel VBA worksheet is an alternative tool for simplifying analytical QM that is effectively controlled and convenient, with multistage SQC designs.