The necessity and appropriate range of the diagnostic "gray zone" of 13C-urea breath test

• Published in: Saudi journal of gastroenterology Vol. 28; no. 5; pp. 385 - 392
• Main Authors: Yin, Zhihao, Xiao, Shiyu, Tian, Xueli, Yuan, Ziying, Zhou, Liya
• Format: Journal Article
• Language: English
• Published: Riyadh Wolters Kluwer India Pvt. Ltd 01.09.2022; Medknow Publications and Media Pvt. Ltd; Medknow Publications & Media Pvt. Ltd; Wolters Kluwer - Medknow; Wolters Kluwer Medknow Publications
• Subjects: 13c-urea breath test; Accuracy; Breath tests; false negative; gray zone; Helicobacter infections; helicobacter pylori; Infection; intestinal metaplasia; Medical research; Medicine, Experimental; Original; Urea; China; helicobacter pylori; gray zone; 13C-urea breath test; false negative; intestinal metaplasia
• ISSN: 1319-3767; 1998-4049
• DOI: 10.4103/sjg.sjg_638_21

Background: The 13C-urea breath test (13C-UBT) is preferred for non-invasive detection of Helicobacter pylori (H. pylori); however, its accuracy drops when results fall between 2‰ and 6‰ (called the gray zone). This study aimed to evaluate the accuracy of 13C-UBT (cut-off point 4‰) between 2‰ and 6‰, find a more appropriate gray zone, and identify the factors influencing 13C-UBT. Methods: Patients with 13C-UBT results 2‰-6‰, over an eight-year period, were studied. H. pylori infection was diagnosed if patients were positive for either Warthin-Starry staining or quantitative real-time polymerase chain reaction (real-time PCR), and excluded if both were negative. Accuracy of 13C-UBT under different cut-off points was calculated, and the factors affecting 13C-UBT were analyzed. Results: A total of 208 patients were included, of whom 129 were H. pylori-positive. Sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of 13C-UBT were 71.32%, 83.54%, 64.08%, and 87.62%, respectively. When the cut-off point was changed to 2.15‰, the NPV of 13C-UBT reached a maximum (76.47%); when the cut-off point was changed to 4.95‰, PPV reached its maximum (93.22%). Therefore, the original gray zone (2‰-6‰) was adjusted to 2‰-4.95‰. Gastric antral intestinal metaplasia (OR = 3.055, 95% CI: 1.003-9.309) was an independent risk factor for false-negative 13C-UBT. Conclusions: Accuracy of 13C-UBT over 2‰-6‰ was poor, and the gray zone was changed to 2‰-4.95‰. 13C-UBT results over 2‰-4.95‰ should be interpreted with caution during mass screening of H. pylori, especially for patients with gastric antral intestinal metaplasia.