Not all labs are the same. When a lab says that it has obtained quality systems registration or certification, it conveys that the organization is following a documented quality system in accordance with the quality system element of standards. But these processes do not normally assess technical competency. Often, auditors used for this process have experience in the business being audited, but they are typically not technical experts.
When a lab says it has received accreditation from a recognized accreditation body, on the other hand, that communicates a stronger message--namely, that the lab has undergone a rigorous process through which an independent, third party has verified the organization's technical competence to perform specific tests, types of tests or calibrations. The preeminent accreditation bodies include the American Association for Laboratory Accreditation (A2LA, Frederick, MD), and the National Voluntary Laboratory Accreditation Program (NVLAP, Gaithersburg, MD). Both of these organizations are signatories to the National Cooperation for Laboratory Accreditation Mutual Recognition Arrangement, having demonstrated compliance with ISO/IEC Guide 58 through peer assessment, and both are internationally recognized.