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Volume 5 · Issue 10 · October 2000


An Overview of the Changes to Guide 25
ISO/IEC 17025: The Standard for Laboratory Competence

By Peter S. Unger

Many organizations that rely on the services of testing and calibration laboratories–especially those required by customers or industry requirements to use laboratories with demonstrated competence–have heard the name ISO/IEC 17025 in the past year. But many are not quite sure what it actually means to them and all other organizations and their customers.

Although ISO/IEC 17025:1999, General requirements for the competence of testing and calibration laboratories, replaces ISO/IEC Guide 25:1990, which had almost the exact same name, it is the first edition published as an International Standard.

This change in status from guide to standard is important, because ISO/IEC 17025 is not only a bona fide standard, but it is being viewed by many as such, whereas Guide 25 was perceived to be only a guide not worthy of being followed. While the automotive industry and some individual companies outside the automotive sector have made use of Guide 25 accreditation (e.g., Shell and DuPont), there are others that have expressed an interest in using ISO/IEC 17025, especially in the food industry. The US Food and Drug Administration (FDA) also has announced it is pursuing accreditation of its labs.

The ISO Committee on Conformity Assessment (CASCO) undertook its revisions of Guide 25 in 1994. Completion of CASCO’s work took five years because the issues that needed to be addressed were many and difficult, but the result is a big improvement.

The standard has been unanimously adopted by more than 45 accreditation bodies that are members of the International Laboratory Accreditation Cooperation (ILAC). These include many European bodies, making ISO/IEC a significant development, since Guide 25 was not used in Europe. European Norm (EN) 45001, which is slightly different from Guide 25, was until recently the standard in use.

ISO/IEC 17025 by itself will also facilitate the effectiveness of the ILAC mutual recognition arrangement (ILAC Arrangement), which is expected to be signed by more than 30 national laboratory accreditation bodies in early November 2000. The ILAC Arrangement will provide a technical underpinning to international trade by promoting cross-border stakeholder confidence and acceptance of accredited laboratory data.

There is no international mutual recognition agreement yet in lab accreditation, which can be a hindrance for some types of international trade. ISO/IEC 17025 and the ILAC Arrangement therefore fill a gap that has long existed.

Scope and Purpose of ISO/IEC 17025

ISO/IEC 17025:1999 is intended primarily for laboratories that wish to demonstrate competence, whether or not they desire accreditation. It also provides uniform general accreditation criteria with numerous explanatory notes to reduce the need for further application documents.

Besides Guide 25, the new standard has replaced the European standard EN45001. It includes new requirements for the development of new methods and method validation and sampling techniques where such developments are relevant to a laboratory’s work. However, ISO/IEC 17025 does not address purely research and development laboratories.

Even though the standard incorporates quality management system (QMS) requirements equivalent to those in ISO 9001/2:1994, it should not be characterized as a laboratory-specific QMS standard.

It was never intended for "certification" in the ISO 9001/2/3 sense of quality system registration. ISO/IEC 17025 includes technical requirements related to laboratory competence to perform specific tests or calibrations. As such, the only suitable form of recognition against it is accreditation for the performing of specific tests or calibrations.

How Does It Differ From Guide 25?

Although there is some debate about what the major differences are between the new standard and the superseded Guide 25, the following paragraphs, numbered to correspond to the requirement sections of ISO/IEC 17025:1999, provide a brief overview of its requirements.

Your organization should actually examine the text of the standard very carefully as a whole unit, especially if it is unfamiliar with Guide 25. There is no simple list from which you can conclude what a laboratory that has conformed to Guide 25 actually needs to change and how to conform to ISO/IEC 17025:1999.

Keep in mind that this overview is designed for those familiar with Guide 25, but it could be helpful for those organizations that use calibration and/or testing laboratories, whether or not they are in industrial sectors where the use of accredited labs is or will be required.

4, Management Requirements

This section does not quite cover the complete requirements of ISO 9001/2:1994. Some elements of ISO 9001/2 are addressed in Section 5, Technical Requirements. Likewise, there are also some "technical" aspects covered in this "management" section.

4.1, Organization

This clause covers ISO/IEC Guide 25:1990 items in a similar way, but less prescriptively. A new requirement is the need for a laboratory to identify any potential conflicts of interest. Clause 4.1 recognizes that a laboratory acts in many ways like a "third party" in that it is not in business to simply satisfy its direct customers (i.e., always giving customers the results they expect), but to provide valid, reliable data upon which appropriate decisions can be made.

4.2, Quality System

Although the list of what the quality manual is required to contain is less prescriptive, the required contents of a laboratory’s quality policy statement are more prescriptive.

4.3, Document Control

More specific requirements are included for the review, approval, issuance and amendment of documents in line with ISO 9001/2:1994.

4.4, Review of Requests, Tender and Contracts

Guide 25’s contract review requirements were "arrangements for handling new work". Those arrangements a laboratory is to have for handling new work have been converted to the ISO 9001/2 requirements, including identification of customer needs, assurance to meet those needs and provision for handling changes or deviations to contracts.

4.5, Subcontracting of Tests and Calibrations

This clause has been expanded to cover permanent subcontracting of parts of the work involved in accredited tests/calibrations, whereas Guide 25 only addressed temporary subcontracting.

4.6, Purchasing Services and Supplies

Quality control of services and supplies–or inputs to a laboratory’s processes affecting the integrity of tests and calibrations–is now covered more comprehensively, but yet in a slightly simpler fashion than ISO 9001/2:1994.

4.7, Service to the Client

This is a new clause with no prior counterpart–Guide 25 did not address communicating with or servicing clients. Cooperation with clients is demanded. Advising clients on what they may really need from the testing to be conducted is also encouraged. This is a notable change. While labs traditionally are not uncooperative, advice has been perceived as potentially representing a conflict of interest, so the new requirements make cooperation and advice required or permissible.

4.8, Complaints

A change is that it is no longer necessary to audit the relevant operations when any complaint raises doubt about the validity of the test/calibration results. Otherwise, the requirements in this clause are equivalent to those in Guide 25.

4.9, Control of Nonconforming Testing and/or Calibration Work

A single requirement for a laboratory to have procedures for control of nonconforming work has been introduced that consolidates and replaces prior requirements found in several clauses of Guide 25.

4.10, Corrective Action

This clause has been upgraded to be in line with ISO 9001/2’s content by requiring procedures to be implemented for cause analysis, selection and implementation of corrective action, subsequent monitoring and follow-up audits.

4.11, Preventive Action

This is a new requirement in line with ISO 9001/2’s content.

4.12, Control of Records

Although very similar to the prior requirements, it is written to be in line with ISO 9001/2’s content. It also addresses electronic records in an up-to-date fashion.

4.13, Internal Audits

Very similar to Guide 25’s requirements, it is in line with ISO 9001/2’s content.

4.14, Management Review

This clause now specifies what must be addressed by management reviews, but the absolute requirement that a lab conduct annual reviews has been transformed into a recommendation contained in a note.

5 Technical Requirements

The technical requirements are described in greater detail than in Guide 25 to ensure more consistent interpretation by laboratories and enlighten the reader about the intentions of the requirements.

5.1, General

This clause lists the factors that determine the correctness and reliability of results and the contributions to the total uncertainty of measurements.

5.2, Personnel

The requirements for personnel competency to be used by a laboratory are much more clearly described. The additional detail has slightly expanded the requirements.

5.3, Accommodations and Environmental Conditions

The requirements in this clause are very similar to those in Guide 25.

5.4, Test and Calibration Methods and Method Validation

This clause is greatly expanded to address nonroutine work, validation of methods and estimation of uncertainty of measurement. Although the measurement uncertainty concept is well known to the calibration community, many fields of testing are unfamiliar with the concept and its application to tests, particularly tests whose results are qualitative. This was the major reason for the US negative vote on the FDIS. Much work is needed to develop examples of how to estimate uncertainty for testing. For this reason, implementation will take more time in some areas. A pragmatic, incremental approach to the implementation of measurement uncertainty is being recommended by many accreditation bodies.

5.5, Equipment

These requirements are much the same as before, except that sampling equipment and borrowed, rented or leased equipment is now explicitly addressed.

5.6, Measurement Traceability

With the exception of Clause 5.10 below, which provides reporting requirements, this clause is the only one that addresses the distinctions between calibration laboratories and testing laboratories. There are eight notes to explain certain aspects of the requirements.

5.7, Sampling

The requirements for sampling are new.

5.8, Handling of Test and Calibration Items

No major changes from Guide 25 are evident.

5.9, Assuring the Quality of Test and Calibration Results

No substantive changes have been made to these requirements.

5.10, Reporting the Results

A great deal more flexibility is allowed a laboratory depending upon whether it issues calibration certificates or reports and/or test reports and whether it services internal or external clients. For internal clients and in the case of written agreements with external clients, the results may be reported in a simplified way. Opinions and interpretations may also be included in a test report if properly identified as such.

Annex A

The first annex provides a table identifying where the different elements of ISO 9001/2:1994 are addressed in ISO/IEC 17025:1999.

Annex B

Guidelines for establishing applications in specific fields are provided, with an admonition that applications should not include additional general requirements.

The Transition to ISO/IEC 17025

Calibration and testing laboratories and their accreditation bodies have entered a period of transition now that ISO/IEC 17025:1999 has been published and updating of the accreditation process is underway. The challenge is for accreditation bodies to revise processes and train staff and assessors on the new standard while laboratories update their quality systems and technical processes to the new and revised requirements. In general, the sooner the transition is completed the better, since the transition period will give rise to two types of accreditation–to the old Guide 25 and the new 17025.

One thing remains clear: if a laboratory is accredited to the criteria of ISO/IEC Guide 25:1990, it remains competent. Only the prerequisites have changed in line with the desire of the community of interests to align management requirements with ISO 9001/2:1994. Most accredited laboratories are expected to conform to ISO/IEC 17025:1999 by 2002. As discussed above, agreed practice for uncertainty estimation may take longer in some fields of testing.

ILAC guidance on ISO/IEC 17025 implementation will be decided at an ILAC General Assembly meeting in November 2000. The current proposal is that, by the end of 2002, all laboratories accredited to Guide 25 must be operating to the new standard and must have been through a surveillance, assessment or re-assessment by their accreditation bodies to confirm compliance.

Very few ISO/IEC 17025 accreditations have been accomplished to date, and laboratories accredited to Guide 25 by the American Association for Laboratory Accreditation (A2LA) have until July 1, 2002, to comply based on a successful on-site assessment.

With completion of ISO/IEC 17025 in 1999 and its linkage to the quality system requirements of ISO 9001/2:1994, the transition to the new standard may barely finish before another transition will begin. Recognizing the impending approval of ISO 9001:2000 in November 2000, CASCO has already started the work of considering an amendment to align ISO/IEC 17025:1999 with ISO 9001:2000. This revision work is clearly not expected to take another six years. A two-year time frame is anticipated, resulting in release of ISO/IEC 17025:2002 that will ensure consistency of the QMS approaches between laboratories and their clients.


The elevation of laboratory competency requirements to the status of an International (ISO/IEC) Standard has already reaped benefits. The misinformed debate about a "standard versus guide" is now over. There is no longer much confusion in the laboratory marketplace as to the imperative nature of the new standard and its use as accreditation criteria.

The widespread and quick adoption of ISO/IEC 17025:1999 by the world’s laboratory accreditation body community and many of their stakeholders has ensured its use and importance as the basis of mutual recognition agreements for facilitating trade. The standard represents a major milestone foreseen 23 years ago at the first International Laboratory Accreditation Conference.

If your organization uses or will need to use laboratories accredited to Guide 25 or ISO/IEC 17025, it is advisable to become familiar with the full text of the new standard. This will help you understand what is or will be required of laboratories to demonstrate competency and in providing services to your organization.

Peter S. Unger is President of A2LA, a nonprofit membership organization that administers the largest general purpose laboratory accreditation system in the United States. He has been involved with national laboratory accreditation since 1978. Prior to attaining his current position in 1996, Mr. Unger served as Vice President of A2LA and was previously Associate Manager of Laboratory Accreditation at the National Bureau of Standards (now the National Institute of Standards and Technology). He is also Chairman of the Mutual Recognition Arrangement Council of the Asia Pacific Laboratory Accreditation Cooperation (APLAC), chairs the Training Committee of the National Cooperation for Laboratory Accreditation (NACLA) and is Convenor of the Working Group on Arrangement Documentation of ILAC. Mr. Unger has a BS degree in systems engineering from Princeton University, a Masters in environmental management from George Washington University, is an RAB-certified lead auditor and is a member of THE OUTLOOK’s Editorial Advisory Board.

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