Blood Test 98% Accurate?

[prinsessa]

DH wasn't too convinced of the results from Enterolab (which were positive), so I agreed to get an opinion from a doctor about our son. Our son is 3 and has only had a few solid BMs his whole life. The only time his BMs got better was after he went gluten free (it has been about a month). He is also on the small side (5% for weight and 10-15% for height) which I think is strange since both DH and I are pretty tall.

His doctor referred him to a Ped GI specialist. I asked the specialist about the blood test results (which were negative) and she said they are 98% accurate. I tried to look for information about it and I didn't see anything like that on the web. The specialist wants to test his stool for parasites. I didn't mention Enterolab because I didn't want her to think I was crazy (like some other people seem to think I am for using them). I also agreed to put him back on gluten so he can get the endoscopy. If he starts getting really sick going back on gluten, I am taking him back off it. His health is more important than what anyone else thinks.

So I guess my original question was....how accurate are the blood tests (especially in children)?

[Rachel--24]

There are people who have negative bloodwork and positive biopsies...I've seen it posted here enough times to question what you're doctor is saying. One reason for false negatives on the bloodwork can be due to IgA deficiency. Was your son's total IgA serum tested? Its part of the celiac panel but many doctors dont order that test.

[CarlaB]

My guess is that your doc has misunderstood the 98% and what it means. I'm not sure, but I'd guess they're 98% accurate when positive ... so, would that be 98% specific? I don't really know for sure, but I have heard that they have a false negative rate, but are usually right when positive. Plus, how did they come to that conclusion? Did 98% of the people who were positive have positive biopsies? I wonder where they get that number from. Once someone told me that statistics were like bikinis .... they showed a lot but could cover what was essential.

As you know, many of us around here have had negative blood work, but gluten makes us ill.

[GFBetsy]

Actually, the most sensitive of the currently used celiac tests is only 86% sensitive. (My husband works in the lab at our regional hospital, and brought home a copy of a story in one of his lab magazines, so that's how I know.) I just went and got my copy of the article. It was in the Medical Laboratory Observer in January of 2006, pages 10 - 13. Here's a link to the article: Open Original Shared Link.

The article is a discussion of whether genetic testing for celiac genes at birth is a wise idea. On page 12, there is a table that lists the sensitivity and specificity of the commonly used tests for celiac. The most sensitive is the Endomysial Antibody, which is no longer used as commonly as the Tissue TransGlutaminase because of the expense, and it is 86% - 100% sensitive. (Which means, as far as I can tell, that the test could pick up celiac 100% of the time, but that it is only guaranteed to do so 86% of the time.) And the TTG and Anti-Gliadin tests are 77-100% sensitive and 52-100% sensitive, respectively. (Of course, it might mean that some of the companies that make the tests make ones that are only 86% sensitive, while others make tests that are 100% sensitive . . . Hmmm. I never thought of that before.)

But, all things considered, I really don't think that your doctor can guarantee that the tests are 98% accurate. I've had doctors tell me the same thing in the past, but I'm pretty sure that they are wrong.

Print a copy of the article and take it to your doctor, if he/she won't believe you any other way.

Good luck!

[Guest nini]

there are entirely too many people who have had negative bloodwork, yet eventually had positive biopsies to take that Dr.s claim seriously. From what I've read (and I'm not a scientist) the testing is extremely unreliable in children and only marginally reliable in adults. Positive if they are positive, but if they are negative it just means that they couldn't find anything. It can never ever rule it out completely.

[Ursa Major]

Prinsessa, at the age of three the biopsy might be negative, too, as the damage might not be bad enough to show. Are you sure you want to actually purposely try to wreck the villi in your son's bowels to try to get a positive biopsy? Do you know that he could get extremely ill, and nobody has done any studies to see if having celiac disease (and the accompanying malabsorption) doesn't cause permanent brain damage in children's developing brains?

In kids that young trying the diet is the most valid test there is. Since he responds well to the gluten-free diet, he obviously shouldn't be eating gluten. Period.

And for the biopsy even having the slightest chance of being accurate, your son would have to eat at least four slices of bread for six months to a year. And even then it might end up being a false negative.

Since the results from Enterolab were positive, he has celiac disease, who cares what your ignorant doctors say.

[tarnalberry]

you can check pubmed for the studies, but I recall studies that note that the expected test result specificity and sensitivity are lower than estimated in the labs when those tests are used in practices. 98% sensitivity just isn't the case in practice.

[moomama18]

exactly what Rachel-24 said. My daughter's blood test came back negative but she had an IgA deficiency. I called Children's Hospital and talked to the clinic - they said that there was definitely a chance that she had Celiac's and her test was a false negative. I think they said there is no such thing as a false positive but plenty of false negatives. Being gluten free - she gained 6 pounds in less than six months, grew hair and had a complete turn around in her personality. She finally slept in HER own bed!!! Best of luck to you!

[bklynceliac]

my understanding with blood test was - and it sounds like others are certainly better informed - that 98% of those who tested positive for Celiac Disease in fact had it. So, the test is considered reliable because of the only 2% false positives. But obviously, that's not very reassuring.

[prinsessa]

Thanks for everyone's replies. I really don't want to have DS go back on gluten. I know I am gluten intolerant even though my blood tests were negative. I am thinking about asking the GI doctor if they could test the fat in his stool (since they are doing a stool test anyway). Then they can test it again once he goes off gluten for a while. It isn't any problem keeping him off gluten since DD and I are gluten free and he isn't in daycare right now.

It is strange that the doctor doesn't know more about gluten intolerance since she said several people in her family have Celiac. She might think that I just want to try some new "fad diet". I just want to make sure my kids are going to grow to be healthy adults. I know parents probably come in with some crazy ideas sometimes, but parents probably also know their kids better than a doctor.

btw, the only thing they tested for was the TTG. Are they supposed to test for more things than that for the blood test?

[Helena]

Yeah, they're supposed to do the EMA test too. Some doctors also do the antigliadin tests . ..

Maybe you should ask for the full celiac panel.

See the Celiac Centre at Columbia for info. on the testing (this might be a good resource to bring in to your doc to explain why you want more tests. Dr. Green is pretty much *the* expert on celiac disease in North America.

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