Mini-Dose (1-μCi) 14-Urea Breath Test for the Detection of Helicobacter pylori

Objectives: To develop and evaluate a mini-dose (1-μ Ci ) ¹⁴C-urea breath test (UBT), using a simplified protocol. Methods: Fasting patients (n = 95) were given a drink of 1 μCi (37 kBq) of ¹⁴C-urea. Samples of breath carbon dioxide (2 mmol) were collected at 10, 20, and 30 min later by trapping in hyamine solution; ¹⁴C activity was measured by liquid scintillation counting. Results were expressed as "CO₂ recovery," i.e ., (% of administered dose recovered/mmol CO₂ trapped) × body weight (kg)]. Reproducibility of the test was assessed by repeat studies on two consecutive days in 11 volunteers. All breath test results were compared with culture for Helicobacter pylori . In 27 patients, results also were compared with ¹³C-urea breath test (European protocol). Results: Using receiver operator characteristic (ROC) analysis, we selected a cut-off value of 0.55 at 20 min to separate those positive and negative for H. pylori . Sensitivity and specificity were 98% and 87%, respectively. Among four patients with negative culture hut positive ¹⁴C-breath tests, three had evidence of infection by serology or ¹³C-UBT. Assuming that these three were genuinely positive, the recalculated specificity improved to 97%, sensitivity remaining at 98%. The reproducibility of the test was good, with only a minor day-to-day variation. Concordance with the ¹³C-UBT was excellent: there was 100% agreement in the diagnostic classification of all 27 patients (19 positive, eight negative). Conclusions: The mini-dose ¹⁴C-urea breath test has a high diagnostic accuracy (sensitivity 98%, specificity 97%) with minimal radiation exposure. It is simple, rapid, and convenient for a busy general hospital.