Proficiency testing in the food microbiology laboratory.

Laboratories offering a quality service for the microbiological examination of food must implement a quality assurance system. An effective system should, in addition to daily quality control of procedures, consumables, and equipment, include external laboratory accreditation to a recognised standard, the use of validated test methods, and participation in an external quality assessment (proficiency testing) scheme. External quality assessment (EQA) is a system in which samples of known but undisclosed content are introduced into a laboratory's routine testing procedure, in other words, a challenge to those procedures. There are a number of EQA schemes available to food microbiology laboratories, either offering freeze dried mixtures of organisms as simulated foods or preweighed portions of spiked dried foods. There are a number of important requirements for an effective EQA scheme and a range of benefits from participation to a laboratory. These are discussed in the light of experience with the development of a specific scheme.