Proficiency testing (PT) programs are used by A2LA as part of the laboratory accreditation assessment process to determine the ability of laboratories to perform competently tests or calibrations for which accreditation is held. Proficiency testing programs are also used to monitor accredited laboratories' continuing performance.

The A2LA Accreditation Program for Providers of Proficiency Testing Programs is designed for proficiency testing providers who wish to demonstrate their competence by formal compliance with a set of internationally-acceptable requirements for the planning and implementation of proficiency testing programs. The program also provides users of proficiency testing programs (laboratories, accreditation bodies such as A2LA, technical assessors, etc.) increased confidence that the PT programs being relied upon are being operated competently in accordance with specified technical and management system requirements.

The specific assessment requirements for this program are based on the requirements contained in the ILAC Guidelines for the Requirements for the Competence of Providers of Proficiency Testing. These requirements are based upon ISO Guide 43-1(1997) and on the relevant elements of ISO/IEC 17025:1999 applicable to characterization, homogeneity, and stability testing of proficiency testing materials. In addition, the relevant ISO 9000 requirements have been included to eliminate the need for a separate recognition of proficiency testing providers for ISO 9000 compliance.

A2LA recommends that wherever possible, A2LA-accredited testing and calibration laboratories use accredited proficiency testing (PT) providers to meet the accreditation requirements for participation in proficiency testing.