Thistle QA is a South African company started by Dr. Jim McCulloch in 1989. Thistle QA commenced proficiency testing (PT) in Johannesburg with a single general chemistry program. The company is now the largest PT provider in southern Africa. Thistle QA, with the support and endorsement of stakeholders and international collaborators, has now expanded the scope of operations to become a full service PT provider.

Thistle QA is a member of the DigitalPT International EQA Collaboration - an active collaboration of PT Providers and their laboratories using the DigitalPT informatics system to share academic and educational resources to improve the global quality of medical testing.