Proficiency testing (PT) is the evaluation of participant performance against pre-established criteria by means of interlaboratory comparisons.

PT providers organise comparative testing schemes that allow laboratories to assess the accuracy and reliability of their results. By analysing the same samples and comparing results across multiple laboratories, proficiency testing helps identify errors, improve performance and ensure consistent quality.

The laboratories, and in some cases inspection bodies, that are assessed and accredited by the accreditation bodies that are members of Global ACI participate in proficiency testing as a requirement for maintaining their accreditation. Many PT providers seek accreditation to ISO/IEC 17043, which specifies the general requirements for the competence and impartiality of PT providers.