2. How are proficiency tests organized?

International standards regulate various aspects of proficiency testing:

• ISO/IEC Guide 43-1: implementation and organization of proficiency testing ;

• ISO/IEC Guide 43-2: Relationship between proficiency testing and certification bodies ;

• ISO 13528: statistical methods for the interpretation of proficiency tests ;

• ISO 17043: requirements for proficiency testing organizers.

In practice, firstly, the participants jointly choose the nature of the tests, the type of material and the interpretation procedures. Then, each year, they receive one or more samples on which they must perform a single measurement using their own method. Often, the circuit covers several analytes. The results are sent back to the organizer,...