Coeliac antibodies

[Caterina0909]

Hello

I have a question about antibody levels... do they remain constant from day to day? If blood was taken on one day and the result was, for example (made up figure) 10, if another blood sample was taken 2 days later (again made up figure) would the result still be 10 or does it vary from day to day?

Thanks :)

[Scott Adams]

I don't recall seeing any studies done that would compare antibody tests on a daily basis, but I believe they are known to be relatively stable. This means that it takes weeks for them to move up or down significantly, so if you've been gluten-free for a year or more you would need to eat gluten daily for at least 6-8 weeks, and perhaps up to 12 weeks, before doing a blood test for celiac disease. After some people go gluten-free it takes them months to get their levels down, but part of that could also be attributed to eating small amounts of contamination, perhaps if they eat in restaurants.

[RMJ]

The longevity of antibodies is measured using a concept called the half life - the length of time it takes for half of the antibodies to disappear from the bloodstream.  Estimates for TTG antibodies are 2 to 6 months.  This means they would remain pretty stable from day to day.

However, there is another reason one might not get the exact same test results from day to day - the reproducibility of the tests.  Test the exact same sample from the same test tube 10 times and you may get (made up figure) 10 most of the time, but sometimes 9, sometimes 11.

[Caterina0909]

Thank-you both. That is super helpful.