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Dear listmembers, about a week ago I posted a question concerning the
reliability of  HLA testing (human leukocyte antigen test). I am very
grateful that you mailed me a lot of answers and questions, which I now will
try to summarize:
My internist in Amsterdam because I live in the Netherlands,  had told me en
passant that a HLA test had proven that celiac disease was ruled out. He had
not told me beforehand that he had ordered this test. So I did not know what
a HLA test was and how reliable it could be.  Because I did not yet asked my
internist about this test I can’t give an answer on the questions some
listmembers asked me which gene my doctor had told me was responsible for
CD.
Verna Boos mailed me that according to the literature around 95 % of people
with celiac have HLA DQ2 or DQ8. That leaves around 5 % that don’t have
either of them and do have celiac. She told me about a new article about HLA
in celiac disease, that appeared in the latest issue of Tissue Antigens.
Fortunately Roy Jamron has put last sunday the address on the list  where
you can download the full text of the article concerned. For a layman it is
no easy stuff to read, but you get a global knowledge about HLA testing and
CD.  Others didn’t know about HLA testing, but were interested, like me, to
hear more about the genetic aspects of CD.
Noah L. Still mailed me that HLA-DQ2-MICB10 is the best predictor of the
disease. ‘Presence of allele 10 of MICB is associated with a more than
5-fold increased risk for celiac disease.’ He continues: CD patients
predominantly inherit HLA-DPB1*0101 positive haplotype from HLA-DQ2
homozygous parent.  A distinct HLA-DQ alpha/beta heterodimer (DQ2) encoded
by the MHC class II DQA1*0501 and the DQB1*02 alleles confers the primary
HLA-associated susceptibility to develop CD.  A minority of patients carries
the DQA1*03-DQB1*0302 haplotype (DQ8). According to him EMA has a better
specificity (90-100%) than other serological tests. Gliadin antibodies are
also to be found in other gastrointestinal, other disorders and in healthy
individuals. Positivity for gliadin antibodies seems to increase with age in
healthy individuals as was found in 10% of healthy population between 60-69
years. He concludes: ‘Presence of the molecularly defined HLA-DQ2 and
HLA-DQ8 is present in more than 99% in CD.  Noah Still does not think that
the total absence of HLA-DQ2 or DQ8 excludes the diagnosis of CD. But wheat
allergy could also be a possibility.
The were more listmembers who suggested a wheat allergy. Kathi Borden had
the same experience like me that she was told she was not CD. Later she had
tests done by dr. Fine in Texas, who examines a stool sample for evidence of
intestinal damage. He concluded she was negative for CD, but should stay
away from gluten and yeast. She had also had a HLA testing done. Dr. Fine
concluded that it was highly unlikely that she had celiac, because she had
not the HLA-DQ2 and/or HLA-DQ8-gene. Later she heard a lecture of Dr.
Alessio Fasano of the CD Research Center of the University of Maryland. Some
listmembers recommended him to me. Fasano told his audience that the
HLA-test is a ‘pretty good’ negative predictor of CD. If you don’t have DQ2
or DQ8 it is highly unlikely that you could have CD.  However, if you have
them it does not mean you automatically have CD, just that you have the
tendency to have it. Kathi: ‘Notice that he didn’t say if you DO NOT have
DQ2 or DQ8 it is IMPOSSIBLE to have it. Only highly unlikely that you don’t.
’ She decided that it is not really important to have a diagnosis if you
know what works for you and I remain glutenfree and symptom-free.
Heidi Schuppenhauer also pointed that about 98 % of people with CD have DQ2
of DQ8 or both. But according to her there are also other kinds of gluten
intolerance. ‘Most of the people who can’t tolerate gluten DO NOT have
“celiac”, which is defined as a certain type of intestinal damage. And the 2
% who definitely have celiac don’t have the genes. ’ This is confirmed by
Deborah Thompson. Her son’s test said that he didn’t have the genetic
markers to indicate that he was susceptible to CD. But he is still
gluten-intolerant, like me. Finally Lillian Horn mailed me that her doctor
says that the HLA test is unreliable and that he won’t do the test. Dear
members, I feel very touched by all your answers, some of which were very
comprehensive and impressive. Good luck to all of you. Johanna Donia

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