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Based on the number of posts recently regarding blood test results, I thought
this reply would be of interest to the entire listserv..

Re: CD blood tests [log in to unmask] writes:

> It seemed that the more I read the more confused I became.

The problem that no test providescan yet provide a black or white
answer...Each test is rated as being both sensitive and specific.

While one aspect of a individual test may catch all with celiac, it may also
catch some who don't have it...false positives.

The other aspect of the same test may be great for excluding those who don't
have have celiac, but might fail to catch every celiac...false negatives.

The ratio of specificity to sensitivity varies from test to test so a
potentially false positive test on one type of test has be balance against the
potentially false negative of another.  Running more tests gives more
variable that
need to be considered--like doing those matrix problems in algebra, except
those had definite solutions.

There is a great article on this at www.celiac.com in the FAQ (frequently
asked questions) section under What is the probability of false positive and
false negative results from the serological tests?** (You will probably
have to
read through this slowly several times it get the gist of it. Then you still
probably won't be able to explain it, but you will begin to understand why the
answers aren't simple.)

In her book Raising our Celiac Kids, Danna Korn has an interesting chart of
the possible combinations of positive & negative values for the various tests
and the likelihood of having celiac.  Of course, I am always reminder of the
punchline from an old CSA cartoon by Sam Hockstra--"With celiac, anything can
happen and usually does..."

And new research is suggesting that the newest bloods tests which catch all
celiacs & exclude those without, may still be related to the degree of GI
damage and those with slight/early damage could still be missed.

Current blood tests of celiac are definitely still a work in process but
better than any available since lots of people can be screened relatively
inexpensively. That's why it is important to have a doctor with lots of
practical
experience in diagnosing celiac or with enough wisdom to realize when
he/she needs
some outside expertise.

It also indicates the importance of a biopsy which can detect various degrees
of damage (again, if it is done & interpreted correctly) if for no other
reason than to provide a benchmark as insurance if symptoms do not resolve
with a
g.f. diet. Comparing a second biopsy to the pre-treatment one can provide
invaluable information in those cases.

Bev in Milwaukee

*Support summarization of posts, reply to the SENDER not the Celiac List*