ISO/IEC 17025:2017, Section 7.7, “Ensuring the validity of results,” is a wonderful tool for laboratories confirming their end data is accurate and reliable. The standard guides the laboratory to develop a procedure to record data and detect and monitor trends. To aid in this goal, the laboratory utilizes reference and quality control materials, performs functional equipment checks, performs replicate testing and retests, and intermediate checks to verify consistency in results.
Proficiency Testing and/or Interlaboratory Comparison (PT/ILC)
Regular participation in proficiency testing and/or interlaboratory comparison (PT/ILC), testing helps a laboratory ensure methods, technicians, and laboratory equipment are performing properly. Proficiency testing provides confidence in the competence of the laboratory by comparing results from numerous laboratories using the same or similar methods of measurement. PT/ILC studies help ensure the methods chosen by the laboratory are truly fit for purpose in the measurements being performed. PT/ILC studies are a great way to ensure technician competency and may pinpoint areas where further training and development may be required.
The laboratory’s participation in PT/ILC studies should be based on good risk management, using risk-based thinking when developing the laboratory’s PT plan. When commercial PT is not available, the ILAC P9 document is an excellent resource for developing an internal PT/ILC program. As a requirement of the laboratory’s accreditation, the full scope of activities should be covered in the laboratory’s four-year PT/ILC plan. A PT/ILC plan needs to cover all major fields on the laboratory’s scope. It is important to consider previous participation and that all qualified analysts participate.
Analyzing Data in PT/ILC Programs
Critically important, the laboratories must analyze the data generated when ensuring the validity of results, as well as the results received from commercial PT activities. Simply gathering the data is not sufficient. The data must be analyzed and used to improve laboratory activities. Good PT/ILC programs will have pre-defined criteria to measure results in a meaningful way. Results that fall outside the predefined criteria must be investigated by the laboratory and may lead to effective corrective action activities. The intent here is to prevent incorrect results from being reported.
When analyzing data, be it PT/ILC results, reference materials, or duplicate testing, the laboratory’s use of control charts to detect and trend data becomes a valuable tool detect trends, assess risk, and work toward continual improvement.
Ensuring validity of results is required for laboratories accredited to ISO/IEC 17025, but the concepts can be applied to any organization generating results. Setting pre-defined criteria to the results of the analysis of data provides a means for evaluating generated data to ensure it is of the appropriate quality. Taking action on results that are found to be outside that pre-defined criteria allows the laboratory to take actions to correct any issues and ensure that incorrect results are not reported to customers.