Microbiological measurement uncertainty

Understand uncertainty in microbiological measurements and how to take account of it to help ensure the reliability of microbiological analyses

No measurement is perfect - it has associated uncertainty arising from many factors. Understanding this uncertainty - its extent, how it arises and how contributing factors affect it - is essential for the correct interpretation of a result, as uncertainty is an important indicator of a measurement's quality. Consequently, ISO 17025* requires laboratories to have and apply procedures for estimating uncertainty of measurement. However, until now there has been little guidance for microbiologists on how they should evaluate measurement uncertainty in microbiological analysis.

This guide is designed to be an easy-to-follow, step-by-step approach to the measurement of uncertainty in microbiological analysis. Produced by a group of industrial microbiologists and data analysts, with a strong emphasis on practical day-to-day application, it includes a spreadsheet to perform the necessary mathematics. It adopts established approaches, which are widely accepted for use by chemists in chemical analysis, and adapts them to microbiological circumstances. It specifically addresses the ISO 17025 requirements to identify and estimate all components of uncertainty. The approach advocated makes optimum use of data generated during routine internal and external laboratory quality assurance, so that many laboratories will find they do not need to conduct extra analyses or generate additional data to make use of the procedures.

*General requirements for the competence of testing and calibration laboratories.

• Scope and field of application
• What is uncertainty?
• Microbiological measurement and uncertainty
• The process of measurement uncertainty evaluation
  - Step 1 - Specification of the measurand
  - Step 2 - Identifying uncertainty sources
  - Step 3 - Quantifying uncertainty
  - Step 4 - Calculating the combined uncertainty
• Reporting uncertainty
• Assessment of compliance with specifications
• Using the spreadsheets
• References

Softcover - 48 pages plus disk*

* One free copy of the spreadsheet is provided with each copy of the guide. Its use requires a PC with Excel and assumes proficiency with this package. The spreadsheet cannot be provided in any other package. CCFRA does not undertake to provide support to users of this spreadsheet and is not able to provide support in the use of Excel. Both the spreadsheet and the guide are protected by copyright law.