Determination of the optimal cut‐off value for the [13C]‐urea breath test based on aHelicobacter pylori‐specific polymerase chain reaction assay

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Abstract
Background : This study was conducted to determine the optimal cut‐off value and breath sample collection time for the [13C]‐urea breath test based on the assessment of Helicobacter pylori status with a gastric juice‐based polymerase chain reaction (PCR) assay. Methods and Results : A total of 104 patients took 100 mg [13C]‐urea orally and breath samples were collected at 5, 10, 20, 30 and 60 min. The increment of 13CO2: 12 CO2 ratio from the baseline (δ 13 C) was measured using a laser spectroanalyser. The PCR assay was positive in 63 and negative in 41 patients. The optimal cut‐off value of δ 13 C was calculated for each sample collection time so that the distance from the geometric mean value among Helicobacter pylori‐positive patients and that from the arithmetic mean value among negative patients were simultaneously maximized. The cut‐off value of 2.7‰ at 20 min had the longest distance, being separated by 3.16 SD from the two mean values. Using this cut‐off value, the urea breath test showed 100% specificity and 98% sensitivity for the diagnosis of Helicobacter pylori infection.