The output of laboratories is critical for those making decisions based on the data they produce. Poor data from laboratories leads to poor decisions which may have catastrophic personal or financial impacts on the people or organizations affected by those decisions. The competence of laboratories to perform specific tests, measurements or calibrations should, therefore, be an issue of fundamental interest to both the clients of laboratories and their own management and staff.

Laboratory accreditation is the process now used comprehensively around the world to provide an independent appraisal and recognition of the specific competence of testing and calibration laboratories.

Laboratory accreditation bodies use a combination of techniques to evaluate the specific technical competence of laboratories, including:

• Internationally-harmonized standards: (ISO/IEC 17025 for most testing and calibration laboratories and ISO 15189 for medical laboratories);

• On-site assessment teams comprising expert assessors with knowledge of the management and technical requirements of the standards as well as technical assessors with specific expertise in the types of tests, measurements or calibrations for which the laboratory seeks recognition of its competence;

• Where possible, proficiency testing (inter-laboratory tests intended to evaluate the laboratories' performance against reference or consensus values for the items involved);

• Ongoing reassessment of laboratories' competence after accreditation.

On achieving accreditation, a laboratory can promote its competence by various means including use of the accreditation body's logo or mark on test or calibration reports. The laboratory's accreditation status is usually published by the accreditation body in its directory and this provides potential clients with full details of the "Scope of accreditation" relevant to each laboratory.

It is important to highlight that accreditation recognizes competence for specific tests or types of tests or measurements. It is not a general endorsement of the capabilities of laboratories to undertake any type of testing, unless that testing is covered by the laboratory's scope of accreditation.

It is also worth noting that the need for recognition of testing competence through accreditation is not restricted to support for test results to facilitate trade. The need for confidence in testing in both developing and developed countries covers all aspect of society: public health, environmental monitoring, forensic services, transport safety, construction, occupational health and safety, defence, communications, domestic trade and commerce, industrial efficiency, agricultural and commodity quality, etc.