Saturday, January 24, 2009
Interpreting Lab Work
Gluten sensitive patients not only have to do their own research regarding their symptoms but they have to self-diagnose and sometimes are forced to interpret their own lab tests!
I just received the following question:
A lady in my group has the following blood work and I need help with
Tissue Transglutaminase AB is 1.2
Endomysial Antibody is Negative
Gliadin IgA is 1
Gliadin IgG is 1
IgA (Immunoglobulin A) is 152
What does this last one mean? Is that a positive reading?
She had been previously diagnosed a few years ago with DH [dermatitis herpetiformis], but the doctor never told her about the GF [gluten-free] diet, so it was just forgotten. Fast forward a few years and now she was diagnosed with MS [multiple sclerosis]. The doctor at the Cleveland Clinic told her she should go on a GF diet because she probably also has celiac.
She met with me to learn about the GF diet. I suggested she get tested
for celiac first, which she did. Soon after she was tested and read the
information I gave her, she read about the DH and then mentioned she
had already been diagnosed with that. The diet is helping, but she would like to
know the meaning of her blood work. It looks to be negative except for the
IgA, but I don't know what the normal range is for that test.
And with DH, can you test negative via regular blood testing? According to
Dr. Green, you can, but I was wondering if anyone has come across this.
She is trying to understand all this and I want to give her the correct information.
What a sad story. I would like to say it’s unique and uncommon but unfortunately quite the opposite is true. The lack of understanding of the damage gluten sensitivity can cause is staggering.
Here’s a woman who several years ago was diagnosed with dermatitis herpetiformis, a very uncomfortable, unsightly skin condition for which the ONLY known treatment IS a gluten-free diet and she is never told about it. Adding insult to injury the gluten she continued to eat may very well be responsible for the autoimmune, degenerative nerve disease she is now diagnosed with, multiple sclerosis.
To answer the question posed regarding lab tests, let’s take them one at a time. First I’d like to mention that if you want accurate data from a doctor regarding a lab result long distance, don’t just include the result itself but also the reference range of the test. Labs differ in this regard and a result is only as valuable as the reference range is also included.
The data below comes from our book, The Gluten Effect – available February 13, 2009.
Anti-tissue Transglutaminase Antibodies - Anti-tissue Transglutaminase Antibodies (tTG antibodies) are auto-antibodies directed against “self” tissue. After gliadin crosses the intestinal lining, a special enzyme called tissue transglutaminase binds to gliadin and takes off a portion of the protein. This portion is called glutamine. tTG antibodies are antibodies that are directed against the complex of gliadin attached to the tissue transglutaminase enzyme. tTG antibodies are 90 percent accurate in Celiac disease because they represent immune system attack at the level of the intestinal lining. Gluten sensitivity that involves minor intestinal injury or no villous atrophy will be less likely detected by tTG antibodies. Therefore, tTG antibodies correlate best with villous atrophy as several studies have supported, and a negative tTG antibody test (or EM antibody test for that matter) does not rule out gluten sensitivity when intestinal involvement is minimal or absent.
Anti-Endomysial Antibodies - Anti-Endomysial Antibodies (EM antibodies) are auto-antibodies. Gliadin is a gluten protein so therefore when the immune system attacks it, is not attacking “self” tissues but instead a foreign food protein. In contrast, as gliadin is absorbed through the intestinal lining, it attaches to the smooth muscle cells of the intestinal wall. EM antibodies are directed against proteins of these smooth muscle cells, and therefore EM antibodies are directed against “self” tissue. This defines them as auto-antibodies.Because EM antibodies attack the smooth muscle of the small intestine, these antibodies correlate better with damage to the intestine wall. Studies have supported an accuracy rate of approximately 90 percent for Celiac disease. Actually in one study, EM antibodies were present in 100 percent of individuals when total villous atrophy was present. However, EM antibodies are ineffective in detecting individuals with silent or subclinical gluten sensitivity. If minor involvement of the intestinal lining occurs or if no intestinal involvement is present, EM antibodies are much less accurate.As with Anti-Gliadin Antibodies, EM antibody testing should evaluate IgG and IgA forms of antibodies. If a gluten sensitive patient is IgA deficient, IgA EM antibodies may be falsely negative even for Celiac disease.
Anti-Gliadin Antibodies - Gliadin is the protein component of gluten that triggers the immune reactions in sensitive people, and therefore many people with gluten sensitivity have antibodies to this protein. Testing for anti-gliadin antibodies (AGA) is a simple blood test, but studies have shown that it is less sensitive for detecting Celiac disease compared to other antibodies. The confusion is that the ability of AGA to detect gluten intolerance has been defined in conjunction with a positive intestinal biopsy. While this may be a standard for Celiac disease, we now know that this is an inaccurate standard for gluten sensitivity. In fact, AGA may be the best current diagnostic test when considering all gluten related disorders. In testing for AGA, antibodies of both the IgG and IgA classes are checked since low total levels of IgA may be present. If a person has low total IgA levels, antibody tests for IgA may be falsely negative.
Total Serum IgA Level - Low total levels of IgA antibodies are rarely found in the normal population with one out of every six hundred people having this condition, but in gluten sensitivity, low IgA levels are more common. This reflects the increased IgA antibody production in the intestine to fight off gluten as it attempts to enter our bodies. If a low level of IgA is present, then certainly IgG varieties of the antibody tests described above will be more accurate in diagnosing gluten related conditions. In general, total IgA levels are not ordered often since IgG antibody tests are usually ordered concurrently. Therefore, defining a low IgA level adds little information in making a diagnosis. There is a general theory however that a lower IgA level suggests greater inflammation of the intestinal lining and greater chronicity of disease. A low IgA level may provide some insight into duration of disease.
A high serum IgA level as seen in the above test is likely indicating an infection. Increased serum IgA is common in skin, gut, respiratory and renal infections. We know this patient has DH so secondary skin infections do make sense.
The reader also asks if blood tests can be negative with DH. Yes they can. Also remember that even those diagnosed with celiac disease via biopsy show negative blood results 15% of the time.
That’s why the moral of the story at this time is to evaluate how you feel when you eat 100% gluten-free for a couple of months. Until we have highly sensitive tests we can rely on to accurately diagnose gluten sensitivity, diagnosing will involve “building a case” by pulling together many pieces of information about the patient including symptoms, response to a gluten-free diet, lab tests, genetic history, presence of intestinal infections, etc.
This leads us to explain some things about this particular patient. She has known DH which is solely due to gluten intolerance, yet it can be present with negative blood tests. Does that make the diagnosis or need for a gluten-free diet in question? Not at all. She is now diagnosed with MS. We know that, second to the digestive tract, the most common system to be affected by gluten is the nervous system with autoimmune diseases occurring at a very high rate. Does the negative test ensure that gluten had nothing to do with the development of MS? No, it doesn’t. We’d need to know a lot more about this patient (which by the way is the most difficult part of hearing from readers long distance – I want more data.) but I wouldn’t be surprised to find other factors which point to gluten as the culprit.
To Your Good Health!
Dr Vikki Petersen