This chapter describes the widely diversified range of conditions that are associated with autoimmune antibodies. Using examples, the concepts involved in understanding the complex relationships between autoantibodies, symptoms and diagnosis are explained. The issues involved due to variation between methods and lack of standardization are reviewed. This chapter includes a comprehensive coverage of autoantibody tests, their clinical applications, assay technology and limitations. They are related to a wide range of clinical conditions. The tests are: anti-nuclear antibodies, anti-DNA, anti-Sm, anti-RNP, anti-SSA/Ro, anti-SSB/La, anti-histone, anti-centromere, anti-Scl-70, IgG ant-RNA polymerase III, rheumatoid factor, anti-cyclic citrullinated peptide, anti-neutrophilic cytoplasmic antibodies, anti-glomerular basement membrane, anti-Jo-1, anti-microsomal antibody, thyroid peroxidase antibody, thyroid-stimulating hormone receptor antibody, islet cell autoantibodies, anti-adrenal cortical antibodies, anti-parietal cell antibodies, anti-intrinsic factor antibodies, anti-mitochondrial antibodies, anti-SMA, anti-LKM, IgA anti-endomysium, IgA anti-tissue transglutaminase, IgG anti-deamidated gliadin, IgA anti-deamidated gliadin, anti-acetylcholine receptor, striational antibodies, calcium channel antibodies, anti-cardiolipin, beta-2 glycoprotein antibodies, neuropathy-associated antibodies, anti-myelin-associated glycoprotein, anti-Hu, anti-Ri,
and Purkinje cell cytoplasmic antibodies. The clinical conditions are: Goodpasture’s syndrome, primary biliary cirrhosis, systemic lupus erythematosus, mixed connective tissue disease, Sjögren’s syndrome, drug-induced lupus, polymyositis, dermatomyositis, Raynaud’s phenomenon, rheumatoid arthritis, CREST, sclerosis, scleroderma, Wegener’s granulomatosis, microscopic polyangitis, Churg-Strauss syndrome, Hashimoto’s thyroiditis, Graves’ disease, diabetes, diabetes mellitus, Addison’s disease, pernicious anemia, cholangitis, autoimmune hepatitis, celiac disease, myasthenia gravis, Lambert-Eaton syndrome, phospholipid antibody syndrome, syphilis, and paraneoplastic syndrome.

Due to the availability of highly specific and sensitive clinical laboratory testing in the past 10-20 years, epidemiologic studies now estimate the incidence of celiac disease as about 1/100 in Western European and Northern American populations (1).  Similar rates have been recorded in many European countries and recent studies in China have found a “growing” rate that may reflect both environmental changes (adopting a more western diet) as well as increased availability of testing (2). Laboratory testing of celiac disease during the first half of the twentieth century consisted of detecting a hypochromic anemia, decreased iron stores, hypocalcemia, and fatty stools. Of course, these findings only identified the most severe cases that occurred in children aged 9 months to 10 years. The death rate among children 2-3 years of age in several studies was as high as 1/3 of the reported cases (3).  After the studies of Dicke et al. determined that it was not carbohydrate, but rather the protein gluten in wheat, barley and rye that triggered the disease, the adoption of a gluten-free diet was able to alleviate the patient in the vast majority of cases (4).

In the 1950s, Margot Shiner devised a biopsy tube that could be passed orally into the small intestine to obtain a “blind” biopsy (5). The hisopathologic findings in active celiac disease were stratified by Marsh (as modified by Oberhuber), allowing grading of the villous atrophy and hyperplasia of the crypts (6).  While these features were characteristic of celiac disease, they were not specific. So, before launching patients on a lifelong journey with a severely restricting diet, Trier devised a strict regimen of testing that greatly improved the specificity of the pathology interpretation of the biopsy (7).

Trier criteria required:

1. A duodenal biopsy with features consistent with celiac disease.
2. The patient was placed on a gluten-free diet.
3. A repeat duodenal biopsy needed to show improvement.
4. The patient was re-challenged with a diet containing gluten.
5. A third duodenal biopsy needed to show recurrent features of celiac disease.

Serologic tests for celiac disease were developed as early as 1964 when Berger et al. reported the demonstration of anti-gliadin antibodies in celiac disease (8).  In 1971, Seah et al. recorded high sensitivity for anti-reticulin antibodies in children with celiac disease (9). Unfortunately, both tests lacked specificity by reacting in many controls and other gastrointestinal disorders, weakening their utility for diagnosing celiac disease. However, three excellent tests have become standard in the past 10-20 years, IgA anti-endomysium (EMA), IgA anti-tissue transglutaminase (tTG), and IgG and IgA anti-deamidated gliadin (DGP) (Table) (10,11).

Serologic Markers of Celiac Disease*

Serologic Test	Sensitivity	Specificity	Main Use
IgA anti-tTG	98 (74-100)	97 (78-100)	Preferred (except in IgA deficient)
IgA anti-EMA	90 (75-96)	98 (91-100)	Best specificity-but is observer dependent
IgG anti-DGP	80.1-98.6	86.0-96.9	More sensitive than tTG in <2yr
IgA anti-DGP	80.7-95.1	86.3-93.1

*Data from Giersiepen et al (11).

As a result of the improved sensitivity and specificity of these newer laboratory tests for celiac disease, the European Society for Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHN) has proclaimed that a biopsy need not be performed in the following situation:

1. A child with suggestive symptoms
2. A consistent HLA haplotype (either HLA-DQ2 or HLA-DQ8)
3. A positive IgA anti-EMA test and
4. A positive IgA anti-tTG with a reactivity >10X the upper limit of normal.

The ESPGHN has found this combination to have almost a 100% positive predictive value for celiac disease (11). This rationale reflects a combination of the marked improvement in serologic testing as well as the continued nonspecificity of the biopsy result (7). Consequently, the risk and cost of the invasive biopsy procedure is no longer clearly superior to the relatively small risk of a false positive result using currently available serologic testing. ESPGHN cautions, however, that these individuals must be closely monitored to assure that overlooked associated conditions such as eosinophilic esophagitis, peptic esophagitis and gastritis are not also present.

Dr. David F. Keren, M.D., is a Professor in the Department of Pathology at the University of Michigan Medical School where he is the Associate Director of the Clinical Pathology Laboratories. His academic interests include the laboratory evaluation of autoimmune diseases, monoclonal gammopathies, hemoglobinopathies and management strategies. Dr. Keren has served as President of the Gastrointestinal Pathology Society, the Michigan Society of Pathologists, the American Society for Clinical Pathology, and the American Board of Pathology. He has authored over 160 peer-reviewed articles, 41 chapters in books, and has written or edited 13 books. He is recipient of the Carl A. Jolliff Award from the Clinical and Diagnostic Immunology Division of the American Association of Clinical Chemists, the Lifetime Achievement Award from the Michigan Society of Pathologists, the Israel Davidsohn Award, the Distinguished Service Award, and the Mastership Award from the American Society for Clinical Pathology.

Autoimmune, autoimmunity, tolerance, indirect immunofluorescence, immunometric, multiplex, line probe assay, immunoblot, flow cytometry, rheumatoid factor, latex agglutination, radioimmunoassay, Goodpasture’s syndrome, primary biliary cirrhosis, systemic lupus erythematosus, mixed connective tissue disease, Sjögren’s syndrome, drug-induced lupus, polymyositis, dermatomyositis, Raynaud’s phenomenon, rheumatoid arthritis, CREST, sclerosis, scleroderma, Wegener’s granulomatosis, microscopic polyangitis, Churg-Strauss syndrome, Hashimoto’s thyroiditis, Graves’ disease, diabetes, diabetes mellitus, Addison’s disease, pernicious anemia, cholangitis, autoimmune hepatitis, celiac disease, myasthenia gravis, Lambert-Eaton syndrome, phospholipid antibody syndrome, syphilis, paraneoplastic syndrome, anti-nuclear antibodies, anti-DNA, anti-Sm, anti-RNP, anti-SSA/Ro, anti-SSB/La, anti-histone, anti-centromere, anti-Scl-70, IgG ant-RNA polymerase III, rheumatoid factor, anti-cyclic citrullinated peptide, anti-neutrophilic cytoplasmic antibodies, anti-glomerular basement membrane, anti-Jo-1, anti-microsomal antibody, thyroid peroxidase antibody, thyroid-stimulating hormone receptor antibody, islet cell autoantibodies, anti-adrenal cortical antibodies, anti-parietal cell antibodies, anti-intrinsic factor antibodies, anti-mitochondrial antibodies, anti-SMA, anti-LKM, IgA anti-endomysium, IgA anti-tissue transglutaminase, IgG anti-deamidated gliadin, IgA anti-deamidated gliadin, anti-acetylcholine receptor, striational antibodies, calcium channel antibodies, anti-cardiolipin, beta-2 glycoprotein antibodies, neuropathy-associated antibodies, anti-myelin-associated glycoprotein, anti-Hu, anti-Ri, Purkinje cell cytoplasmic antibodies.