Iron and Vitamin B12 Deficiency in Patients with Autoimmune Gastritis and <i>Helicobacter pylori</i> Gastritis: Results from a Prospective Multicenter Study

<b><i>Introduction:</i></b> Iron and vitamin B12 deficiencies are common in patients with atrophic gastritis, but there are limited data on the prevalence of these deficiencies in different types of atrophic gastritis. <b><i>Methods:</i></b> This multicenter, prospective study assessed micronutrient concentrations in histologically confirmed autoimmune gastritis (AIG, <i>n</i> = 45), <i>Helicobacter pylori-</i>related non-autoimmune gastritis (NAIG, <i>n</i> = 109), and control patients (<i>n</i> = 201). A multivariate analysis was performed to determine factors influencing those deficiencies. <b><i>Results:</i></b> The median vitamin B12 concentration was significantly lower in AIG (367.5 pg/mL, Q1, Q3: 235.5, 524.5) than in NAIG (445.0 pg/mL, Q1, Q3: 355.0, 565.0, <i>p</i> = 0.001) and control patients (391.0 pg/mL, Q1, Q3: 323.5, 488.7, <i>p</i> = 0.001). Vitamin B12 deficiency was found in 13.3%, 1.5%, and 2.8% of AIG, NAIG, and control patients, respectively. Similarly, the median ferritin concentration was significantly lower in AIG (39.5 ng/mL, Q1, Q3: 15.4, 98.3 ng/mL) than in NAIG (80.5 ng/mL, Q1, Q3: 43.6, 133.9, <i>p</i> = 0.04) and control patients (66.5 ng/mL, Q1, Q3: 33.4, 119.8, <i>p</i> = 0.007). Iron deficiency and iron deficiency adjusted to CRP were present in 28.9% and 33.3% of AIG, 12.8% and 16.5% of NAIG, and 12.9% and 18.4% of controls, respectively. Multivariate analysis demonstrated that AIG patients had a higher risk of developing vitamin B12 deficiency (OR: 11.52 [2.85–57.64, <i>p</i> = 0.001]) and iron deficiency (OR: 2.92 [1.32–6.30, <i>p</i> = 0.007]) compared to control patients. Factors like age, sex, and <i>H. pylori</i> status did not affect the occurrence of vitamin B12 or iron deficiency. <b><i>Conclusion:</i></b> Iron and vitamin B12 deficiencies are more commonly observed in patients with AIG than in those with NAIG or control patients. Therefore, it is essential to screen for both iron and vitamin B12 deficiencies in AIG patients and include the treatment of micronutrient deficiencies in the management of atrophic gastritis patients.