So...if you still want to get the test to confirm if you need a stronger dose or to eliminate the med, I have another idea.
Have your GI write a letter to your carrier explaining the purpose of the test is to modify the Humira dosage for approriate care. if thye note that it could prevent you from needing a larger dose or could remove you from the drug, it may make the carrier reconsider the value of the test. If your doc can prove medical necessity while pointing out potential cost savings, it may change the opinion of the carrier. I am not promising anything here, but it does happen. (Heck I did this for a simple 3.58 bill on a vitamin that was not OTC so ti was easy, but I have seen other tx arguments carry)