The antibodies of the calibrators, positive control, and diluted patient samples react with fragments of deamidated gliadin immobilized on the solid phase of microtiter plates. After an incubation period of 60 min at room temperature (18...25°C), unbound serum components are removed by a wash step. The bound autoantibodies react specifically with anti-human-IgA-antibodies conjugated to horseradish peroxidase (HRP) within the incubation period of 30 min at room temperature. Excessive conjugate is separated from the solid-phase immune complexes by the following wash step. HRP converts the colorless substrate solution of 3,3',5,5'-tetramethyl benzidine (TMB) added into a blue product. This enzyme reaction is stopped by dispensing an acidic solution (H2SO4) into the wells after 15 min at room temperature turning the solution from blue to yellow. The optical density (OD) of the solution at 450 nm is directly proportional to the amount of specific antibodies bound. The standard curve is established by plotting the concentrations of the antibodies of the calibrators (x-axis) and their corresponding OD values (y-axis) measured. The concentration of antibodies of the specimen is directly read off the standard curve. Evaluating the test by a semi-quantitative method is also possible. Sample Types: serum, plasma. Range: 10-300 U/mL. Sensitivity: 10 U/mL. Time: 2 hours ? Celiac disease (CD, sprue, gluten enteropathy) is an intolerance to gluten, a cereal protein present primarily in wheat. This gluten-induced enteropathy leads to a severe damage of the small intestine and a so-called ``flat'' mucosa. Due to this extensive lesions mal-absorption occurs accompanied with a depletion of key nutrients.