Tissue Transglutaminase IgA and IgG Correlation with Histology and their Role in a ‘Celiac Panel’; an Institutional Experience Shana Godfred-Cato, DO, PGY-2, Eduardo Castro-Echeverry, MD, MPH, Muralidhar Jatla,MD, Samira Armin, MD, William Koss, MD, and Diana Woodward, MT(ASCP), Chief Technologist, S&W Immunology Lab Scott & White Hospital and Texas A&M Health Sciences Center College of Medicine, Temple, TX Introduction Results Celiac disease is a gastrointestinal disease that affects approximately 1% of the population. The gold standard testing for celiac disease is an intestinal biopsy. Some patients may not or cannot undergo a biopsy so laboratory testing can be a substitute. Tissue transglutaminase (TTG) IgA and IgG are available serologies to screen for celiac disease. A diagnostic challenge can occur in IgA competent patients with TTG IgG positivity but TTG IgA negativity. We assessed the correlation of TTG IgA and IgG with histology while trying to choose an accurate and cost effective “celiac panel” for a large integrated healthcare organization. 2464 patients had negative (93.8%) celiac antibodies (TTG IgA-/TTG IgG-). 163 patients tested positive (6.2%). 26 patients were TTG IgA+/TTG IgG+; of these, 9 patients were not biopsied, 2 were unknown and 15 underwent biopsy with 12 of those having a positive biopsy (80%). 28 patients were TTG IgA+/TTG IgG-; of these, 16 were not biopsied and 12 underwent biopsied, with 7 of those having a positive biopsy (58%). 109 patients were TTG IgA-/TTG IgG+; of these, 67 patients were not biopsied, 7 were unknown and 35 underwent biopsy, with 1 of those having a positive biopsy (2.9%). Among TTG IgA-/TTG IgG+ patients, 47 did not have an IgA level checked whereas 62 had an IgA level drawn yielding 60 normal IgA levels and 2 low IgA levels. Abstract Conclusions Tissue transglutaminase (TTG) IgA and IgG can screen for celiac disease (CD). Uncertainty can occur with TTG IgG positivity but TTG IgA negativity.  We assessed the correlation of TTG IgA and IgG with histology while evaluating a “celiac panel” for our institution. Charts of patients for whom celiac disease was suspected over the last year were reviewed.  Data included age, TTG IgG, TTG IgA, serum IgA levels and biopsies. We analyzed correlation of laboratory testing with histology. Three categories of TTG ‘positive’ patients were formed (IgA+/IgG+, IgA+/IgG-, and IgA-/IgG+).  2464 patients were reviewed. We found TTG IgG positivity alone to not be a useful screen for CD as only 2.3% of patients with TTG IgA-/IgG+ had a positive biopsy. TTG IgA levels alone or TTG IgG and IgA together appear to more effectively screen for CD. TTG IgG positivity alone does not appear to be a useful screen for generalized celiac disease screening. In instances of isolated IgG positivity, a higher pre-test probability as determined by clinical findings is required to justify performing a biopsy.   TTG IgA and TTG IgG double positivity can increase the pre-biopsy likelihood of celiac disease.   Patients that have IgA deficiency do not have a reliable TTG IgA level and in that particular case TTG IgG can serve as a useful screen. Patients with normal IgA levels may not benefit from routine TTG IgG screening. TTG IgA and IgA levels together are an effective first screening tool for celiac disease. If IgA deficiency is found then, determining TTG IgG level may provide diagnostic assistance. Our institution has decided to use TTG IgA and IgA level as an initial screening tool for celiac disease for patients of all ages. Negative Celiac Biopsy Positive Celiac Biopsy Description of study References We retrospectively reviewed patient charts for those suspected of having celiac disease in the last 12 months at our institution. Data collected included age, TTG IgG levels, TTG IgA levels, serum IgA levels and biopsy results if available. We analyzed correlation of celiac laboratory testing with histology. 3 groups of TTG ‘positive’ patients were identified based on laboratory results (IgA+/IgG+, IgA+/IgG-, and IgA-/IgG+) of 2627 patients overall. Rozenberg, O., Lerner, A., Pacht, A., Grinberg, M., Reginashivili, D., Henig, C., & Barak, M. (2011). A new algorithm for the diagnosis of celiac disease. Cellular & Molecular immunology, 8, 146-149. Brusca, I., Carroccio, A., Tonutti, E., Villalta, D., Tozzoli, R., Barrale, M., Sarullo, F., & Mansueto, P. et al. (2012). The old and new tests for celiac disease: which is the best test combination to diagnose celiac disease in pediatric patients?. Clin chem lab med, 50(1), 111-117. Rozenberg, O., Lerner, A., Pacht, A., Grinberg, M., Reginashivili, D., Henig, C., & Barak, M., (2012). A novel algorithm for the diagnosis of celiac disease and a comprehensive review of celiac disease diagnostics. Clinical rev allerg immunol, 42, 331-341. Rostom, A., Murray, J., & Kagnoff, M., (2006). American Gastroenterological Association (AGA) Institute Technical Review on the Diagnosis and Management of Celiac Disease. Gastroenterology, 131: 1981-2002 Texas Pediatric Society Electronic Poster Contest