Autoantibodies to parietal cells as predictors of atrophic body gastritis: a five-year prospective study in patients with autoimmune thyroid diseases.

Autoimmune thyroid diseases (AITD) can be associated with autoimmune gastritis (AIG), but the frequency of this association is poorly characterized. We performed a prospective study to: a) characterize the frequency of parietal cell (PCA) and intrinsic factor (IFA) autoantibodies in AITD patients; b) evaluate the development of histologically- and functionally-proven AIG after five years and to assess the predictive role of PCA for AIG at baseline; and c) analyze the trend of PCA levels in the course of the disease. We studied 208 consecutive adult patients affected by AITD (166 Hashimoto's thyroiditis, 42 Graves' disease). PCA, IFA and plasma gastrin levels were measured with ELISA methods at baseline and after 5years. At baseline, 51/208 (24.5%) AITD patients were positive for PCA and 10/208 (4.8%) for IFA. 25 out of 54 PCA/IFA-positive AITD patients (all without gastric or haematologic symptoms) agreed to participate in the follow-up study. After 5years, 6 (24%) of these 25 patients showed a histologically proven AIG, with lymphocytic infiltration and/or atrophy of body gastric mucosa. The trend analysis of PCA concentration showed that autoantibody levels rise progressively over time, reach a peak level and then fall, according to the progressive destruction of gastric mucosa and to the disappearance of the target autoantigen (proton pump). The presence of PCA predicts the development of autoimmune gastritis in AITD patients. Antibody levels measured with a sensitive quantitative immunometric method are useful for early diagnosis and early treatment of the disease.