I should have looked at NDAppy's link but if he is AQHA they can get funny about the labs. They will mail you a kit with instructions from their approved lab and the paper work. I want to say it is $40. Worth it not to hassle with whether or not the lab you choose is acceptable and all the other rings I'm sure they'd throw at you.
AQHA requires members to use UCDavis in order for them to "recognize" the results and the test is $40. Horse Tests If AQHA they WILL require testing before registration to note in the papers. Other registers do not (which IMPO is asinine).