Having been down the road of testing, waiting for results, and then not fully understanding the results and their implications, I thought I might try to clear something up -- particularly with regard to my own diagnosis of celiac disease.
There are several standard tests that should be performed as part of a celiac panel. First, serology tests look for three antibodies that are usually found in celiac patients and should ideally be done at the same time. These tests include:
- anti-tissue transglutaminase (tTG) antibodies
- endomysial antibodies (EMA)
- antigliadin antibodies (AGA)
If any of these indicate the possible presence of celiac, then you automatically become a candidate for a small intestinal biopsy, which, according to most doctors, is the only true defininitive way to diagnose celiac disease. And of course, ideally, these tests
must be done before there is any change to your gluten diet.
The
NDDIK (National Institute of Diabetes and Digestive and Kidney Diseases) and NIH (National Institute of Health) states:
"The most sensitive antibody tests are of the immunoglobulin A (IgA) class, but immunoglobulin G (IgG) tests may be used in patients with IgA deficiency. Because no one serologic test is ideal, panels are often used. However, the tests included in a celiac panel vary by lab and may include one or more that are unwarranted. The American Gastroenterological Association recommends beginning with tTG in the clinical setting."
In my personal case, I went gluten-free for almost a week before I could get into the clinic to talk to anybody about my idea of the posssibility that gluten might be making me sick. Armed with information printed from the NIDDK and NIH, I saw a nurse practitioner, she read the information, and told me to go back on gluten for the weekend and then we would take the tTG Antibody test because it was supposed to have a success rate of 95%. Afterall,
"tTG is released from the damaged intestine during active celiac disease, and antibodies to TTG are found to be elevated in the blood of most patients with untreated celiac disease" (Dr. Sheila Crowe,
New York Times, Jan. 12, 2010).
The EMA test listed above isn't as sensitive as the tTG, but it is highly speicific for celiac, with close to a 100% accuracy. Many medical providers don't always choose this test because it is more expensive and time-consuming and is also subject to interpretation by whoever is reading the results. Additionally, when combined with the results of a tTG,
people with a milder case of celiac may go unnoticed. Regardless, I never received this test.
The AGA test is not normally used because it just doesn't seem to be as sensitive or specific enough to used routinely but come in handy for very small children and babies who might otherwise end up with false negative results with the other tests.
Genetic testing is another way to identify specific genes which may determine your likelihood of having celiac, whether you are exhibiting any symptoms or not. It is widely accepted that those people with celiac have the genetic material or human leukocyte antigen (
HLA) or something called
HLA-DQ2 or
HLA-DQ8. The complicated part is that almost half of all Americans will have this in common and not necessarily have celiac disease (
NIDDK). So it would have to be used in conjunction with other tests, particularly if a family member has been diagnosed with celiac and you want to know if you might end up with it sooner or later.
Well, the tests mentioned above are certainly not the end of the story.
I failed the tTG Antibody test. My results showed < 1.2 while the standard for diagnosis is 4 or greater. Naturally, in a test with such high rate of accuracy, I assumed I must not have celiac disease and maybe I was just gluten intolerent.
I was wrong to make that assumption, and several medical providers continued to tell me the same thing. I
should have had the whole panel of tests done, not just the one, and I should not have stopped eating gluten before approaching the clinic with my self-diagnosis. At the time, I was just so happy to be feeling better-- and coupled with my own ignorance, I really didn't care. I was feeling better, and that's all that mattered at the time! But alas, I am not a medical professional, and didn't know any better.
So why was my tTG negative? I don't know what second test was used during my last visit to the ER but the doctor mentioned it would show antibodies for celiac if I had it, and it, too, was negative. Of course, I had been gluten free for quite a while when the blood was drawn, so it didn't surprise me that it might be negative. The ER doctor told me that because my symptoms were cross-organ and cross-systems in the body, that the brain was calling the shots and I was probably just anxious. That was at the tail end of my frustration, for lack of a nicer term...
There is something called
IgA Deficiciency (Immunoglobulin Antibodies), and somewhere
"between 2 and 3 percent of celiac patients have selective IgA deficiency" (NIDDK), and
if the tTG or EMA are negative but celiac still likely, then the IgA levels should be measured. Mine never were tested.
So what is Selective IgA Deficiency? If you are deficient in IgA, then you are deficient in immunoglobulin antibodies. The "anti-self" anitobodies are anti-endomysial and anti-tissue transglutaminase IgA (
American Celiac.org)-- the latter is usually abbreviated tTG. Mine was negative, or "normal" which I took to mean that I didn't have celiac, right?
Wrong.
"To help prevent false negatives, most laboratories will measure the total IgA level at the same time as the TTG IgA level. If you are IgA deficient, then your total IgA level will be very low, and that means there’s a very good chance that the TTG IgA test will be inaccurate (falsely low or normal) because you can’t make IgA antibodies to TTG or gliadin. In this case, your doctor will need to proceed to intestinal biopsies to confirm the suspicion of celiac disease. Occasionally your doctor may order other blood tests, such as TTG IgG or DGP IgG, if they are available" (Crowe, NYT)
According to
Immune Disease.com:
"IgA antibodies are transported in secretions to mucosal surfaces and play a major role in protecting these surfaces from infection. Other immunoglobulin classes are also found in secretions at mucosal surfaces, but not in nearly the same amount as IgA. This is why IgA is known as the secretory antibody. If our mucosal surfaces were spread out they would cover an area equal to one and one-half tennis courts, so the importance of IgA in protecting our mucosal surfaces cannot be overstated."
Just because you may not be producing enough IgA, however, does not mean your body is falling apart and you're not producing others to help your body function. In fact, that is why they call is
"Selective IgA Deficiency." Nobody really knows why or how IgA deficiency happens, but it can be quite common.
So what does IgA deficincy have to do with me? Well, it could be
one reason why my blood tests were normal, and it could also explain my susceptability to respiratory infections which have plagued me most of my life-- everything from chronic allergies, sinusitis, bronchitis, ear infections (as a child), and pneumonia.
"Studies have indicated that as many as one in every five hundred people have Selective IgA Deficiency. Many of these individuals appear healthy, or have relatively mild illnesses and are generally not sick enough to be seen by a doctor and may never be discovered to have IgA deficiency" (Immune Disease.com), but is "much more common in those with celiac disease" (Crowe, NYT).
Though I have not experienced food allergies that I know of (knock on wood), food allergies are also associated with IgA deficiencies.
"Symptoms associated with food allergies are diarrhea or abdominal cramping. It is not certain whether there is an increased incidence of allergic rhinitis (hay fever) or eczema in Selective IgA Deficiency" (Immune Disease.com)
Well, it certainly wouldn't surprise me!!
Another aspect of IgA deficiency includes gastrointestinal infections and chronic diarrhea which I did not experience, at least not enough for me to notice. These illnesses occur because IgA protects the mucosal surfaces, and so without it, we become much more susceptible to infection, and in turn, longer periods of antibiotic treatments, which I still immensely disklike.
So how do you diagnose IgA Deficiency? Well, if you have any of the symptoms I have discussed above, you are probably a candidate for testing-- with or without a celiac disease diagnosis. The test is done through a blood sample, and is often done with a complete blood count (CBC), measurement of lung function, and a urinaylsis (Immune Disease.com):
"Other tests that may be obtained in specific patients include measurement of thyroid function, measurement of kidney function, measurements of absorption of nutrients by the GI tract, and the test for antibodies directed against the body’s own tissues (autoantibodies)."
Currently, there really isn't any treatment for low IgA, but in my case, it might just help to answer a few more questions. If I get an infection (kidney or otherwise), I take appropriate antibiotics, whether I like it or not. If I don't repond well to the antibiotic (which I apparently don't always), there is the alternate possibility of "replacement gamma globulin" (Immune Diseases.com).
During this research I also learned why my allergy shots I took for so many years didn't work. According to the Immune Disease website,
"It is not known whether immunotherapy (allergy shots) is helpful in the allergies associated with Selective IgA Deficiency, although there is no evidence of any increased risk associated with this therapy in these patients." Hmmm....
What to do about an IgA Deficiency? Stay in touch with your doctor. You don't want to end up with problems later down the road for something else that crops up due to a low or non-existent IgA. It could even progress to something called Common Variable Immunodeficiency, which in part, according to the
Merck Manual, sounds suspiciously like celiac diease.
The moral of my story this time is that the IgA Deficiency may have led these high-accuracy tests to yield false negative results which is one of the reasons why that test
should not be performed alone, such as was mine. Additionally, a person has to be eating a lot of gluten (not just a little or some, but a lot) at the time the test is performed. The "weekend" that I added gluten back into my diet was
not a gluten-filled weekend. In fact, I was eating minimal amounts because it was a Christmas week ahead and there were many recitals and things I needed to attend to and did not want to be sick to my stomach during that week. I felt if I ate a couple of pieces of bread, I was okay. Again, in my own ignorance,
I was wrong. Also, if there has been less damage to the small intestine (a lesser degree of villous atrophy), the test may be negative.
And what does all this have to do with
dermatitis herpetiformis? I never had the small intestinal biopsy
because I have dermatitis herpetiformis. According to the New York Times and Dr. Sheila Crowe (a professor in the division of gastroenterology and hepatology in the department of medicine at the University of Virginia), the
"exception to this rule occurs when a patient has a skin condition known as dermatitis herpetiformis, in which case a characteristically abnormal skin biopsy result can subsitute for checking intestinal biopsies" (
New York Times). This was also confirmed by my doctor, who has been the most helpful in diciphering all the clues and helping me understand my diagnosis.
So I don't know if I am actually IgA deficient, but it sounds like it might be a good thing to know, particularly in the long run. It does raise another question for me which I can probably answer myself: Would an IgA Deficiency improve with a gluten-free diet? My answer: probably not.
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