Response to comment on: “decreased titer of anti-parietal cell antibody in advanced phase of autoimmune gastritis”

We thank Dr. Guo and colleagues for their interest in our article, and we appreciate their comments. In our study, autoimmune gastritis (AIG) progressed from the early to end phases, with a subsequent significant decrease in the anti-parietal cell antibody (APCA) titer. A negative APCA could occur, especially in the end phase [1]. In Guo et al.’s report, the change in APCA levels was modest, although 10 of the 16 patients showed a decrease in APCA levels [2]. The difference between those results and the results of the present study may be due to differences in the patient backgrounds, especially the disease phase and age. In our study, 2 of the 44 patients were in the early phase, 11 were in the florid phase, and 31 were in the end phase. Conversely, in Guo et al.’s report, 5 of the 16 patients were in the early phase; 10 were in the florid phase, and only 1 was in the end phase. Based on the natural history of AIG, gastric parietal cells decrease and finally disappear according to the progression from the florid phase to the end phase [3,4]. The APCA titer theoretically decreases according to the disappearance of the proton pump as the target autoantigen, especially in the end phase. In our study, the end phase was dominant, so the decrease of APCA titer may have been detected easily. In Guo et al.’s report, the mean age was 55.8 ± 13.1 years, and the mean follow-up time was 4.5 (range: 2–7) years. In our study, the mean age was 65.0 ± 12.4 years (range 45–84), and relatively old. Conti et al. reported that approximately 20% of patients with AIG were seronegative, and this was more common in elderly patients. Furthermore, a significant inverse correlation was observed between age at the time of AIG diagnosis and the APCA titer [5]. In our study, the majority of patients were elderly, so the decrease in the APCA titer may have been detected easily. As for the decrease in APCA titer in the advanced phase of AIG, future studies with a larger cohort and longitudinal follow-up data are needed.