I am a certified MA. Certification is national, not state-by-state. The offices for Medical Assistant Certification is in Chicago.
The person who is stating that they are certified should have a card stating the date that they became certified and the date that the certification expires from the AAMA (American Association of Medical Assistants). Medical Assistants are given specific guidelines for CEU's that are to be earned during the 5 years that their certification is valid. If CEU's are not received then the MA must re-take the certification exam every 5 years.
Also, you could contact the school that they attended since the school sets up the certification exams and has the information of who has passed/failed.