A combination of serum anti‐Helicobacter pylori antibody titer and Kyoto classification score could provide a more accurate diagnosis of H pylori

Background We previously showed that the endoscopic Kyoto classification for gastritis could predict Helicobacter pylori infection in individuals with a high negative titer of serum anti‐H pylori antibodies. This study evaluated H pylori infection and the Kyoto classification score in patients with a low negative titer (<3 U/ml), high negative titer (3–9.9 U/ml), low positive titer (10–49.9 U/ml), and high positive titer (≥50 U/ml). Methods Serum antibody levels, Kyoto classification score and histology were investigated in 870 individuals with no history of H pylori‐eradication therapy. Urea breath tests (UBTs) were additionally conducted for patients with a low negative titer and a Kyoto score ≥1 or an antibody titer ≥10 U/ml and a Kyoto score of 0 or 1. UBTs and/or histological studies were conducted for participants with a high negative titer. Results False diagnoses based on anti‐H pylori antibody titers were observed in 0.3% of the low‐negative‐titer group, 11.7% of the high‐negative‐titer group, 18.9% of the low‐positive‐titer group and 2.2% of the high‐positive‐titer group. Surprisingly, false diagnoses based on antibody titers were noted in 63.2% of patients with a low positive titer and a Kyoto score of 0 and in 62.5% of patients with a high negative titer and a Kyoto score ≥2, respectively. Conclusions Endoscopic findings could predict false diagnoses determined using serum antibody titers.