Basic Method Validation is part of a trilogy of “back to basics” books that focus on analytical quality management. The other two books are Basic QC Practices and Basic Planning for Quality. When I teach these materials, I start with method validation because it introduces the basic concepts of analytical performance and the experimental and statistical techniques needed to describe performance in quantitative terms. These concepts carry through into the practice of QC and the selection of optimal QC procedures via quality design and planning.
The original source of this approach to method validation goes back thirty years to a series of papers that were published in the American Journal of Medical Technology and later as a monograph titled Method Evaluation. My co-authors were Diane J de Vos, Marian R. Hunt, Else F. Quam, R. Neill Carey, and Carl C. Garber, all of whom worked at the University of Wisconsin. We introduced this approach at workshops that were taught at the national ASMT and AACC meetings. Today Neill and Carl, together with David Koch, continue to teach this approach at the AACC national meeting. They now hold the record for the longest running workshop in AACC history.
This third edition provides important updates based on new regulatory requirements and emerging standards of practice, particularly the latest guidelines from CLSI (Clinical and Laboratory Standards Institute):
• Updated CLIA regulations and accreditation requirements;
• Revised chapter on reportable range that includes calibration verification;
• Revised chapter on detection limits that includes concepts of Limit of Blank, Limit of Detection, and Limit of Quantitation, as recommended in the CLSI EP17 guideline;
• Updated “Method Decision Chart” that includes criteria for 2, 3, 4, 5, and 6-Sigma performance;
• New chapter on estimation of trueness and precision based on the CLSI EP15-A2 guideline, including directions for performing the required calculations using electronic spreadsheets;
• New chapter on evolving global standards (ISO, International Organization for Standardization), ISO 15189, and the concepts of trueness and measurement uncertainty.
• New chapter on Six Sigma metrics, including instructions on how to convert method validation data into Sigma metrics.
For more than thirty years, I have worked on quality control and method validation. While statistics, equations and calculations may not change, the context and the environment are constantly evolving. I hope this third edition helps you understand these method validation numbers in the proper context of your laboratory.
James O. Westgard
Madison Wisconsin
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