How can I evaluate the competency and expertise of a Gastrointestinal CCRN test-taker in a particular medical discipline?

How can I evaluate the competency and expertise of a Gastrointestinal CCRN test-taker in a particular medical discipline? (http://www.cerephon.com/dokumentation/p1242_1429.pdf) A Gastrointestinal CCRN test-taker shall be examined by a medical hygienist to determine whether he/she is qualified to perform the specific