13C urea breath test for Helicobacter pylori:: Determination of the optimal cut-off point in a Canadian community population

AIM: To determine the test characteristics and the optimal cut-off point for the C-13 urea breath test (C-13 UBT) in a Canadian community laboratory setting. METHODS: Of 2232 patients (mean age +/- SD: 51 +/- 21 years, 56% female) who completed a C-13 UBT, 1209 were tested to evaluate the primary diagnosis of Helicobacter pylori infection and 1023 were tested for confirmation of eradication following, treatment. Cloister analysis was performed on the C-13 UBT data to determine the optimal cut-off point and the risk of false-positive and false-negative results. additionally, 176 patients underwent endoscopic biopsy to allow validation of the sensitivity and specificity of the C-13 UBT against histology and microbiology using the calculated cut-off point. RESULTS: The calculated cut-off points were 3.09 delta parts per thousand for the whole Study population (n=2232), 3.09 delta parts per thousand for the diagnosis group (n=1209) and 2.88 delta parts per thousand for the post-treatment group (n=1023). When replacing the calculated cut-off points by a practical cut-off point of 3.0 delta parts per thousand the risk of fake-positive and false-negative results was lower than 2.3%. The C-13 UBT showed 100% sensitivity and 98.5% specificity compared with histology and microbiology (n=176) for the diagnosis of active H pylori infection. CONCLUSIONS: The C-13 UBT is an accurate, noninvasive test for the diagnosis of H pylori infection and for confirmation of cure after eradication therapy. The present study confirms the validity of a cutoff point of 3.0 delta parts per thousand for the C-13 UBT when used in a large Canadian community population according to a standard protocol.