The impact of gastroscopy on the results of ¹³C-urea breath test: a prospective study

The ¹³C-urea breath test (¹³C-UBT) is the gold standard for non-invasive diagnosis of Helicobacter pylori (Hp) infection. However, whether undergoing gastroscopy affects the subsequent ¹³C-UBT results remains unclear. This prospective study aimed to evaluate the impact of gastroscopy on the diagnostic accuracy of follow-up ¹³C-UBT. This prospective, single-center, observational trial enrolled patients aged 18–75 years with positive ¹³C-UBT results within the preceding 4 weeks who were scheduled for gastroscopy. Key procedural variables—including pre-endoscopic ¹³C-UBT delta over baseline (DOB) value, total intraoperative saline irrigation volume, procedure duration, time interval to repeat ¹³C-UBT, and biopsy performance—were recorded. The primary outcome was the conversion of ¹³C-UBT results from positive to negative after gastroscopy. Multivariate Firth logistic regression was performed to identify independent factors associated with conversion. Among 93 enrolled patients, 12 (12.9%) converted to negative on repeat ¹³C-UBT. In univariate analysis, total irrigation volume was significantly higher in the non-conversion group compared with the conversion group (100.0 [60.0-115.0] vs. 60.0 [35.0–90.0] mL, P = 0.009), and the baseline DOB value was significantly lower in the conversion group than in the non-conversion group (6.4 [4.7–8.4] vs. 27.9 [15.3–43.3] ‰, P < 0.001). No significant differences were observed in age, sex, procedure duration, retesting interval and biopsy rate between groups. In multivariate Firth logistic regression, a higher baseline DOB value was an independent factor associated with a lower probability of conversion (OR = 0.739, 95% CI: 0.616–0.885, P = 0.001), whereas irrigation volume was no longer significant (OR = 0.989, 95% CI: 0.969–1.010, P = 0.311). A lower baseline DOB value was an independent factor for negative conversion on subsequent ¹³C-UBT. These findings highlight the need for careful interpretation of post-gastroscopy ¹³C-UBT results, particularly in patients with test values near the diagnostic threshold. The trial was registered in the Chinese Clinical Trial Registry ( www.chictr.org.cn ; No. ChiCTR2400079505) on January 4, 2024.