Re: What is "Participation in interlaboratory comparison or proficiency-testing progr
First contact the agency you are going to obtain your laboratory accreditaiton. They will have a list of proficiency test programs or program organizers that they recognize that have proficiency tests related to your scope. Second contact that proficiency program organizer and see what it will take to join their proficiency test program. Third sign up for a test or two, receive the samples, run the test, submit the data, and review the results report - note you may have to conduct a corrective action and run the test over again in order to come into the acceptable value range for the sample sent to you.
Alternatively if your lab belongs to an organization that has several like labs, look to see if they have a round robin test every once in awhile. This will be where the organization goes to a manufacturer and has the manufacturer build sample(s) of a typical product all of the labs will see. The sample(s) are sent to all the labs at one time or sent to lab 1 who then sends it to lab 2 who then sends it to lab 3, etc. This method is good if you have at least 10 or more similar labs.
Sometimes the standard writing organizations may have a round robin to confirm a test method. This may include some government owned labs.
Be aware not every type of test is able to have round robins or proficiency testing other than the individuals in your lab taking training which includes a test that is graded.