Mini-dose (1-microCi) 14C-urea breath test for the detection of Helicobacter pylori

Abstract

Objectives: To develop and evaluate a mini-dose (1-microCi) 14C-urea breath test (UBT), using a simplified protocol.

Methods: Fasting patients (n = 95) were given a drink of 1 microCi (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) x 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 but 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.