Blood Tests And False Negative Results

[jwblue]

I understand this is a difficult question to answer.

I am asking people to answer this based on their own experience and research.

Assume I have Celiac.

What is the percentage chance that I take a blood test and the result is a false negative?

[nvsmom]

I have seen it written here, and elsewhere, that there is a 25% false negative rate. Other tests I've seen have said much lower but I'm afraid I am unsure what is correct. My tTg IgA and EMA were very positive so I wasn't faced with that issue.

I do know that if you are in the early stages of the disease, a child, or IgA deficient, you are much more likely to test negative. If you have the biopsy, some people have patchier damage than others and it would be easier to miss. Also some people do not present with intestinal symptoms, so they could have a "false negative" to the diet because some changes aren't noticeable for months (like new hair growing in or slow to heal neurological problems).

Good luck.

[GottaSki]

Assume I have Celiac.

What is the percentage chance that I take a blood test and the result is a false negative?

You are asking a lot of good questions - this is a very helpful thing when going through the celiac diagnosis process.

Depending on which antibody test you are talking about this figure changes. I believe current numbers are as high as 30% false negative.

I also believe very strongly that these numbers will change as more and more people are tested for Celiac by both blood and endoscopic biopsy. To date there is a huge number of people that are never tested for Celiac Disease as most doctors are not looking for the Celiac in folks that present with many of the 300+ symptoms associated with Celiac, rather than the shorter list of "classic" symptoms. AND if they test sero-negative are told they do not have Celiac Disease without endoscopic biopsy.

It's all relative. In my family we currently have a 80% false negative blood test rate - if my arithmetic is correct this morning.

5 celiac = 4 sero negative + 1 weak/mild positive

plus one other NCGI or Celiac - to be determined someday - maybe - he is on the fence as to whether he wants to do a gluten challenge - mostly because the rest of us didn't show strong positive blood work.

[jwblue]

If I have Celiac and test false negative, would taking a blood test a second time increase the chance of an accurate diagnosis?

Or is there something in my blood that would cause a false negative making it not beneficial to take a second blood test.

[kareng]

Here is some info that is easy to find from reputable sources:

Open Original Shared Link

How accurate are the celiac blood tests?

The current diagnostic tests for celiac disease are very accurate, particularly when tTG and anti-endomysial antibodies are elevated. The isolated presence of anti-gliadin antibodies does not necessarily imply that the subject is affected by celiac disease, with the exception of children under the age of 2 in which tTG and EMA may not be present

　

Open Original Shared Link

In blood tests, are false positives less common than false negatives?

Even though blood tests are quite accurate, they are falsely positive 1-3% of the time (i.e., being positive without the person having celiac) and, although less commonly, falsely negative 1-2% of the time (i.e., being normal when a person actually has celiac

　

Open Original Shared Link

Is it possible to have a negative blood test, but a positive biopsy?

While rare, it is possible to have a negative blood test and still have celiac disease. tTG sensitivity is approximately 98%, which means that 2% of all celiacs may have a normal tTG level. Sometimes tTG antibodies are not produced enough to show up in the blood stream and can only be detected in the intestinal mucosa by special means.

IgA deficiency is a reason why you might have a negative blood test, but a positive biopsy.

Further medical evaluation is important for anyone still experiencing symptoms in order to establish the diagnosis or to rule out celiac disease as a part of establishing another diagnosis. In some cases, celiac disease is the wrong diagnosis as such conditions as Crohn’s Disease and food protein allergy share many of the same symptoms.

　

[Celiac Mindwarp]

I wonder if the figures above assume you are consuming a gluten full diet at time of testing?

It seems to get more complex if you throw in gluten-free and gluten light.

[kareng]

I wonder if the figures above assume you are consuming a gluten full diet at time of testing?

It seems to get more complex if you throw in gluten-free and gluten light.

I think that is for an average person eating a diet with gluten. They have a recommendation for if you have been gluten-free.

Open Original Shared Link

I’ve heard that I don’t necessarily have to endure 12 weeks of eating gluten if I have a severe reaction. Is that true? How does it work?

The gut needs time to mount an antibody response that can be measured in the blood, which is why we recommend 12 weeks of eating gluten. If you experience symptoms immediately, it’s likely that the gut itself has quickly become damaged. In these cases, you and your medical professional could consider a shorter gluten challenge (3-4 days) and then have a biopsy.

Diagnosis is not an exact science, each person responds differently to the presence of gluten in the small intestine and the amount of time it has been there. Be sure to work with your medical professional to adjust your diet, if needed, during your gluten challenge.

[jwblue]

Here is some info that is easy to find from reputable sources:

Open Original Shared Link

How accurate are the celiac blood tests?

The current diagnostic tests for celiac disease are very accurate, particularly when tTG and anti-endomysial antibodies are elevated. The isolated presence of anti-gliadin antibodies does not necessarily imply that the subject is affected by celiac disease, with the exception of children under the age of 2 in which tTG and EMA may not be present

　

Open Original Shared Link

In blood tests, are false positives less common than false negatives?

Even though blood tests are quite accurate, they are falsely positive 1-3% of the time (i.e., being positive without the person having celiac) and, although less commonly, falsely negative 1-2% of the time (i.e., being normal when a person actually has celiac

　

Open Original Shared Link

Is it possible to have a negative blood test, but a positive biopsy?

While rare, it is possible to have a negative blood test and still have celiac disease. tTG sensitivity is approximately 98%, which means that 2% of all celiacs may have a normal tTG level. Sometimes tTG antibodies are not produced enough to show up in the blood stream and can only be detected in the intestinal mucosa by special means.

IgA deficiency is a reason why you might have a negative blood test, but a positive biopsy.

Further medical evaluation is important for anyone still experiencing symptoms in order to establish the diagnosis or to rule out celiac disease as a part of establishing another diagnosis. In some cases, celiac disease is the wrong diagnosis as such conditions as Crohn’s Disease and food protein allergy share many of the same symptoms.

　

It looks like blood tests are more reliable than most people believe.

[kareng]

It looks like blood tests are more reliable than most people believe.

I wish they would be more specific on which blood tests. I know some docs and labs are not always running the recommended tests and they may not be as accurate as some of the newer tests.

Open Original Shared Link

'Which blood tests should I have to screen for celiac disease?

You should have both tTG-IgA and total serum IgA tests to screen for celiac disease. As long as you produce IgA (total serum IgA confirms you do), tTG-IgA is 98% accurate in measuring elevated antibodies. If IgA deficient, or if there is some other equivocating factor to potentially compromise the blood test, then an EMA blood test is also given.

Other gliadin antibody tests are not useful in screening for celiac disease."

Like I said before, this info is very easy to find . Just google "Celiac centers".

[ravenwoodglass]

I think another variable is which body systems are the most severely or earliest impacted. I showed false negative blood work repeatedly even after my GI system was severely compromised. I do not know if a total IGA was ever done as I was diagnosed many years ago and was seeing many different doctors for different system impacts. Since I had false negative blood tests (the older ones of course) doctors did not even consider doing an endo. I did however have brain lesions that would have been diagnostic if only the doctors had been savvy enough to recognize them for what they were.

I have DH so we know for sure that I have been celiac since childhood but the most severe symptoms that I had for years were neuro and skin related. I had celiac for over 30 years before gut impact became more than an occasional inconvience.

Since so many doctors consider celiac to mainly be a GI related disorder rather than the autoimmune disorder that it is there may be folks that are considered to have false positive tests because their biopsies are negative.

In my own family after I was finally diagnosed both children showed positive on blood work and one on the endo. They never would have even been checked for celiac if I hadn't insisted because I knew it was genetic.

[megsybeth]

I think I read the 1-2% fasle negative statistic on the University of Chicago website but my general experience has not been that doctors test properly. I'd easily believe that half the doctors do the wrong tests or insufficient numbers of tests which would make this number a bit larger. My son was first flagged for celiac because of failure to thrive at 18 months and was told that he tested negative. After looking back through his records I see that he wasn't given a blood test at all for celiac (blood work was done for other things), they based it on assessing fats in the stool, which is not an accepted means. A second doctor did the same at age 2.5. This is a little more extreme, but plenty of adults are given the wrong or insufficient blood tests and told they are negative.

And then there is lab error, lack of skill in the technician. I think the reason these tests are sent out from most labs is that it takes some subjective skill at reading the tests, it's not as clear as a strep culture or something. So I suspect the 1-2% is what a researcher would find in a study of their patients tested by skilled pathologists, with results scored by skilled technicians. I'm very skeptical that this reflects most people's care.

[jwblue]

I think I read the 1-2% fasle negative statistic on the University of Chicago website but my general experience has not been that doctors test properly. I'd easily believe that half the doctors do the wrong tests or insufficient numbers of tests which would make this number a bit larger. My son was first flagged for celiac because of failure to thrive at 18 months and was told that he tested negative. After looking back through his records I see that he wasn't given a blood test at all for celiac (blood work was done for other things), they based it on assessing fats in the stool, which is not an accepted means. A second doctor did the same at age 2.5. This is a little more extreme, but plenty of adults are given the wrong or insufficient blood tests and told they are negative.

And then there is lab error, lack of skill in the technician. I think the reason these tests are sent out from most labs is that it takes some subjective skill at reading the tests, it's not as clear as a strep culture or something. So I suspect the 1-2% is what a researcher would find in a study of their patients tested by skilled pathologists, with results scored by skilled technicians. I'm very skeptical that this reflects most people's care.

Is it possible to take the test result to a second pathologist for a second opinion?

If so, how?

I wonder if their is a higher chance of accuracy if I have the blood test at a hospital lab as opposed to

a Lab Corp or Quest Diagnostics. I am wondering if the technicians and pathologists might be more skilled at a hospital.

Common sense tells me that the answer to this question is yes.