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I recently posted:

"There have been several recent references to stool testing as a  
diagnostic test for celiac disease but I have yet to see a single  
reference to a peer-reviewed article in a reputable scientific journal  
documenting the efficacy of such testing. Without publication in a  
peer-reviewed scientific journal there can be no basis for believing  
that such testing is credible."

Not surprisingly, there were quite a few responses and they fell into  
three main categories.

1) Cheers for posting what should be obvious.

2) Jeers from people who felt that they or a loved one had been let  
down by conventional medicine because they had difficulty getting a  
timely diagnosis or any diagnosis at all and who turned to stool  
testing as an alternative. Having had difficulty getting a diagnosis  
myself, I feel a kinship with these people. The first  
gastroenterologist I saw in the early 90's refused to test for CD when  
I suggested it because "virtually no one in the U.S. has CD". Doctors  
are taught in medical school to look for the most obvious diagnosis.  
Fortunately, the recent prevalence study is changing the perception  
that CD is rare and more doctors are willing to consider testing for CD.

Where I part company with stool test proponents is their willingness  
to advocate for an unproven, undocumented test when proven, well  
documented tests are readily available. They can believe whatever they  
want, however, it does a disservice to those who come to this forum  
for help to recommend unproven testing when proven tests are  
available. That said, no test is perfect. All tests have some level of  
false positives and false negatives. There are good and bad labs and  
good and bad technicians and even the best technician has a bad day.  
Given a choice, however, between documented tests with high  
sensitivities and specificities or undocumented tests,  I find it  
difficult to understand why rational people would choose the latter.

3) References to publications on to stool testing. There were two  
reports that antibodies to gliaden can be found in stool samples (a  
and b below). This should come as no surprise since whatever is shed  
in the intestine will likely wind up in the stool. But, remember to be  
useful, a test must be predictive. Neither study measured the  
specificity and sensitivity of the tests. Sensitivity and specificity  
are the measures used to document the efficacy of a test.

-Sensitivity measures the probability of a positive test among  
patients with a disease.

-Specificity measures the probability of a negative test among  
patients without disease.

One study of children (c) did measure the sensitivity and specificity  
of stool tests for gliaden antibodies, IgA and tTG and found "Neither  
stool test was suitable for screening for coeliac disease in children  
with symptoms." The sensitivity - probability of a positive test in a  
person with disease - to tTG was only 10% and for IgA, only 6%.  
Specificities - probabilities of negative tests among patients without  
disease - were high in both cases. In simple terms, this means that  
while you can test for antibodies in stool, the tests are pretty  
meaningless. On the other hand, there is a great deal of documentation  
for the validity of tTG and IgA blood tests. See (d) for an example.



Happy holidays, Joel

References:
a) http://snipurl.com/1vu8j
b) http://snipurl.com/1vu8m
c) http://snipurl.com/1vu8q
d) http://snipurl.com/1vuai

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