ISO/IEC 17025:2005, Section 5.4.5 requires that methods are validated, and “…that the validation shall be as extensive as is necessary to meet the needs of the given application or field of application”. Further, the standard requires that the laboratory record the validation results, the procedure used for the validation, and a statement as to whether the method is fit for the intended use. The list of methods that require validation include non-standard methods, laboratory-designed/developed methods, standard methods used outside their intended scope, and amplifications and modifications of standard methods. But, what about “standard methods”?
The requirements for “standard methods” can be found in Section 5.4.2 of ISO/IEC 17025, where it states “…the laboratory shall confirm that it can properly operate standard methods before introducing the tests or calibrations. If the standard method changes, the confirmation shall be repeated”. The word “confirmation” can also be used synonymously with “verification”. So, while the terms “validation” and “verification” are often used interchangeably, “verification” has evolved to mean that a laboratory demonstrates that a validated reference method is performing as it should in a laboratory. “Validation”, on the other hand, generally refers to a more rigorous approach to ensuring that a method is fit-for-purpose.
Some of the CALA checklists (e.g., A03 - Rating Guide Appendix, A24 – CALA Checklist for Microbiology) do provide guidance on expectations with respect to validation/verification requirements (e.g., bias, precision, measurement uncertainty, method detection limits, etc…). Generally speaking, most laboratories that are using standard reference methods, demonstrating that the method meets these few performance characteristics verifies that the method is performing satisfactorily and is sufficient evidence to demonstrate that the laboratory conforms to the standard.
However, these key items are not meant to be an exhaustive list of the type and level of validation required to demonstrate that a method is fit-for-purpose. As soon as there is a major change to the method or the method is being used for a matrix for which the reference method was never validated, it is the responsibility of the laboratory to undertake this validation. The type and level of validation required to demonstrate that the method is fit-for-purpose goes above and beyond the few performance characteristics mentioned on the checklist. For example, if a reference method for coliforms in drinking water analysis is being used to analyse soil samples, it would be expected that the laboratory undertake studies on specificity, sensitivity, repeatability, reproducibility or cross validation with another standard method.
More direction on validation can be found in the following documents:
- ISO/IEC 17025:2005 General Requirements for the Competence of Testing and Calibration Laboratories
- P07 – CALA Application of Requirement in ISO/IEC 17025:2005 (http://www.cala.ca/P07-CALA_Application.pdf)
The Fitness for Purpose of Analytical Methods
- A12 – CALA Policy on Reference Methods
Training on Method Validation
The CALA Method Validation course will give you the skills and knowledge required to select appropriate methods, understand, implement and confirm the operation of standard methods, develop in-house methods, validate methods and manage the processes involved.
CALA Training also has webinars that provide an overview of method validation, and details on tools that can be used for method validation.