IgA is the antibody that protects the linings of the gut, airways and other mucous membranes. A total IgA level is measured alongside celiac antibody tests because those tests depend on IgA being present.
Its main job in a celiac screen is quality control: if total IgA is very low (IgA deficiency), the tTG IgA celiac test can read falsely negative and an IgG-based test is needed instead. IgA deficiency is also associated with more frequent respiratory and gut infections.
Optimal Total IgA (Immunoglobulin A): 70-400 mg/dL.
Typically re-tested every 52 weeks.