Ttg Test Results Negative...

[Marz]

IgA TTg - 1.4 (Ref 0.0 - 6 negative, > 6 positive)

IgG TTg - 0.4 (Ref 0.0 - 7 negative, > 7 positive)

Um, I'm not 100% sure which is which, the first might be IgG not IgA, since the results were dictated over the phone...

That's after 3 weeks gluten-free, so I guess not really an accurate result

So over-all result negative, anti-gliadin IgA was also a very low negative (after being a few days gluten-free, that was a few weeks ago), and total IgA levels normal. Dr GI wants to do an in-depth endoscopy taking biopsies throughout the SI, but if I went that route I'd force myself to eat lots of gluten for a month to get the damage back up.

To be honest, even a negative biopsy wouldn't stop me from being gluten-free, so at this point further testing/glutening is just to *prove* that I have textbook celiac disease, which really isn't worth it

Just curious though - the ttg antibodies, why would a "normal" person even have a single antibody for this, why is the reference range so high? Is there really so much "noise" in the test, that they need to set the bar high? Is the 1.4 level I have something indicating a possible issue, even if it's "low" according to the reference range?

[Skylark]

Just curious though - the ttg antibodies, why would a "normal" person even have a single antibody for this, why is the reference range so high? Is there really so much "noise" in the test, that they need to set the bar high? Is the 1.4 level I have something indicating a possible issue, even if it's "low" according to the reference range?

Yes, it's noise. There are lots of sources of noise in clinical assays, including proteins and enzymes in plasma, traces of hemolyzed blood, or slight antibody cross-reactivity. The reference ranges are set to be above the normal amount of noise in the assay. In an assay like this, your reading of 1.4 means the result is completely indistinguishable from the normal assay background.

Out of curiosity what makes you think the top of the reference range is "high"? These tests are set in arbitrary units.

[nora-n]

they set the reference range so high so they supposedly get no negative biopsies if the ttg test is positive.....

There was an article here in celiac.com where real blood samples from biopsy proven celiacs were sent to several actual labs.

Some found most of them, (80% I think)

some only found 50% of them

[Marz]

Out of curiosity what makes you think the top of the reference range is "high"? These tests are set in arbitrary units.

Just high compared to my result Thanks for explaining the reference ranges

[Marz]

they set the reference range so high so they supposedly get no negative biopsies if the ttg test is positive.....

There was an article here in celiac.com where real blood samples from biopsy proven celiacs were sent to several actual labs.

Some found most of them, (80% I think)

some only found 50% of them

Thanks for the info. So the result can vary somewhat depending on the technician's skill or laboratory?

[Skylark]

Thanks for the info. So the result can vary somewhat depending on the technician's skill or laboratory?

Yes, it can. Diagnostic labs usually use automated equipment so technician skill doesn't affect things much, although it can in assays like anti-EMA that are run and read by hand. Variability tends to have more to do with equipment age and brand, batches of assay reagents (this can be a really big factor), blood sample handling, and the details of how that particular lab runs their assays. Some assays are simply less reliable than others too. You're going to get better measurements from lab to lab on a simple test like sodium than on an antibody test where there are multiple biological reagents involved. Also the units in which answers are reported can be different from lab to lab. That's why the more knowledgeable members here will not try to interpret a clinical lab result without a reference range.