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  • Scott Adams
    Scott Adams
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    What is the probability of false positive and false negative results from the serological tests?**

    Vijay Kumar, M.D., Research Associate Professor at the University of Buffalo and President and Director of IMMCO Diagnostics: The three serological tests that are used for diagnosing celiac disease are:

    • Anti-endomysial antibody (EMA)
    • Anti-reticulin antibody (ARA)
    • Anti-gliadin antibody (AGA)

    Each of these three tests provide a certain degree of reliability for diagnosing celiac disease. Of these, endomysial antibody is the most specific test. The following table is taken from our studies (Lerner, Kumar, Iancu, Immunological diagnosis of childhood coeliac disease: comparison between antigliadin, antireticulin and antiendomysial antibodies).

      % of Sensitivity % of Specificity Predictive Value % Pos Predictive Value % Neg
    EMA 97% 98% 97% 98%
    ARA 65% 100% 100% 72%
    IgG AGA 88% 92% 88% 92%
    IgA AGA 52% 94% 87% 74%

     

    The following definitions related to sensitivity, specificity, positive and negative predictive values may help:

    Sensitivity is the probability of a positive test result in a patient with disease. Specificity is the probability of negative test result in a patient without disease. Positive predictive value is the probability of disease in a patient with positive test result. Negative predictive value is the probability of no disease in a patient with negative test result.

    Karoly Horvath, M.D., Ph.D., Associate Professor of Pediatrics; Director, Peds GI & Nutrition Laboratory; University of Maryland at Baltimore: The summary below shows the results of the main serological tests based on several publications including 388 patients with celiac disease, and 771 healthy subjects.

     

    SENSITIVITY- the proportion of subjects with the disease who have a positive test. It indicates how good a test is at identifying the diseased:

      Percentage of - IgA AGA Percentage of - IgG AGA Percentage of - IgA EMA
    Average 78% 79% 97%
    Range 46-100% 57-94% 89-100%



    SPECIFICITY- the proportion of subjects without the disease who have a negative test. It indicates how good a test is at identifying the non-diseased:

      Percentage of - IgA AGA Percentage of - IgG AGA Percentage of - IgA EMA
    Average 92% 84% 98.5%
    Range 84-100% 52-98% 97-100%



    POSITIVE PREDICTIVE VALUE- the probability that a person with positive results actually has the disease:

      Percentage of - IgA AGA Percentage of - IgG AGA Percentage of - IgA EMA
    Average 72% 57% 92%
    Range 45-100% 42-76% 91-94%



    NEGATIVE PREDICTIVE VALUE- the probability that a person with negative results does not have the disease:

      Percentage of - IgA AGA Percentage of - IgG AGA Percentage of - IgA EMA
    Average 94% 94% 100%
    Range 89-100% 83-99% 100%



    References:
    McMillan SA, Haughton DJ, Biggart JD, Edgar JD, Porter KG, McNeill TA. Predictive value for coeliac disease of antibodies to gliadin, endomysium, and jejunum in patients attending for jejunal biopsy. Brit Med J 1991;303:1163-1165
    Ferreira M, Lloyd Davies S, Butler M, Scott D, Clark M, Kumar P. Endomysial antibody: is it the best screening test for coeliac disease? Gut 1992;33:1633-1637.
    Khoshoo V, Bhan MK, Puri S, Jain R, Jayashree S, Bhatnagar S, Kumar R, Stintzing G. Serum antigliadin antibody profile in childhood protracted diarrhea due to coeliac disease and other causes in a developing country. Scand J Gastroenterol 1989;24:1212-1216.
    Chan KN, Phillips AD, Mirakian R, Walker-Smith JA. Endomysial antibody screening in children. J Pediatr Gastroenterol Nutr 1994;18:316-320.
    Bode S, Weile B, Krasilnikoff PA, Gdmand-Hyer E. The diagnostic value of the gliadin antibody testing celiac disease in children: a prospective study. J Pediatr Gastroenterol Nutr 1993;17:260-264.
    Calabuig M, Torregosa R, Polo P, Tom s C, Alvarez V, Garcia-Vila A, Brines J, Vilar P, Farr C, Varea V. Serological markers and celiac disease: a new diagnostic approach ? J Pediatr Gastroenterol Nutr 1990;10:435-442.

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    Not a bad article but missing one important bit of information. Patient can be iga deficient and that would result in possible false negative results on IGA EGA, IGA ARA and IGA EME. Reflecting that a small intestinal biopsy would be the best approach.

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  • About Me

    In 1994 I was diagnosed with celiac disease, which led me to create Celiac.com in 1995. I created this site for a single purpose: To help as many people as possible with celiac disease get diagnosed so they can begin to live happy, healthy gluten-free lives. Celiac.com was the first site on the Internet dedicated solely to celiac disease. In 1998 I founded The Gluten-Free Mall, Your Special Diet Superstore!, and I am the co-author of the book Cereal Killers, and founder and publisher of Journal of Gluten Sensitivity.

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    Scott Adams
    The common list of forbidden grains is: wheat, rye, barley and oats.
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    Scott Adams
    Vijay Kumar, M.D., Research Associate Professor at the University of Buffalo and President and Director of IMMCO Diagnostics: If the test is negative and there is a strong suspicion of celiac disease, it must be repeated after several weeks (3-4 weeks), especially after a high gluten intake. We did a study of two cases with DH who were serologically negative. However, a gluten challenge 1g/Kg body wt/day resulted in positive serology; the results became normal on a gluten free diet.
    If you are a relative of a celiac disease patient and are on a regular diet and the serology performed by an experienced laboratory is negative then there may not be any need for retesting until and unless clinically justified.
    Karoly Horvath, M.D., Ph.D., Associate Professor of Pediatrics; Director, Peds GI & Nutrition Laboratory; University of Maryland at Baltimore: There is no rule for it. If a family member with previous negative tests experiences any gastrointestinal symptoms associated with celiac disease, he/she should undergo serological testing as soon as possible. It is well known that up to 15% of the family members of a patient with celiac disease may have the asymptomatic (latent or silent) form of celiac disease, although they have positive serological tests and have the pathological changes in the upper part of the small intestine. It is also evident that there are at least three developmental stages of mucosal lesions (Marsh MN. Gastroenterology 1992;102:330-354) and celiac disease may manifest at each period of life. That is why we recommend a repeat test every 2-3 years in first degree relatives of celiac patients.

    Scott Adams
    Most of the wheat grain and of white flour is made up of starch granules. Starch granules make up about 75% of grain or of white flour. In the processes used to make wheat starch, a small amount of the gluten protein (actually mostly the gliadin fraction, but not entirely), sticks to the surface of the starch granules. The amount depends on the washing method, how many times the granules are washed, and factors like that. Wheat starch can be made very low in surface protein and it is only the surface protein that is of concern (there are some internal granule proteins, but we are pretty sure that they are not gluten proteins).
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    Scott Adams
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