Improving the Diagnosis of Autoimmune Gastritis: From Parietal Cell Antibodies to H+/K+ ATPase Antibodies.

Parietal cell autoantibodies (PCAs), which recognize the enzyme H+/K+-ATPase as a target, are considered to be a diagnostic marker of autoimmune gastritis and pernicious anemia; these conditions are characterized by the presence of corpus atrophic gastritis. Circulating PCAs can be detected using several analytical methods that are commonly available in the clinical laboratory. Traditionally, indirect immunofluorescence (IIF) on rodent or primate stomach tissue is used as a screening test for the detection of PCAs. However, IIF suffers from a high inter-observer variability and lacks standardization. In addition, like immunoblotting, results are expressed only in a qualitative or semi-quantitative manner. Based on the few available studies that are reviewed herein, quantitative enzyme-linked immunosorbent assays (ELISAs) and fluorescence enzyme immunoassays (FEIAs) using purified H+/K+-ATPase perform better than IIF in the detection of PCAs, displaying higher sensitivity and utility in monitoring the disease. In light of their higher diagnostic accuracy, these solid-phase methods should be preferred to IIF in the screening of autoimmune atrophic gastritis. The use of methods to detect antibodies versus a specific subunit of H+/K+-ATPase (α or β) is currently confined to the world of research. Further investigation is required to define the clinical utility of H+/K+-ATPase subunit detection.