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Joe Murray's comments are appropriate. Intestinal permeability testing
is a good way to answer the question, "Who does NOT have  CD?" and also
"How well is this person's CD doing, how closely is a GF diet being
followed, how completely is the intestine being healed?" In the context
of making a diagnosis of CD, a normal test result is more useful than
an abnormal test result, because a normal result in an untreated person
makes a diagnosis of CD highly unlikely, whether or not the individual
has diarrhea or other obvious intestinal symptoms. In a person known to
have CD, either a normal or abnormal result is useful, especially if
serial measurements are done over time, because the intestinal
permeability test is probably the most sensitive test for measuring the
effects of the damage done by CD.
Leo Galland.