Optimization of ¹³C-urea breath test threshold levels for the detection of Helicobacter pylori infection in a national referral laboratory

Background: Threshold values for ¹³C-urea breath test (13C-UBT) positivity may be affected by various sociodemographic, host, bacterial, and laboratory factors. Manufacturer recommended cutoffs for 13C-UBT assays may not be applicable in all settings. Optimizing 13C-UBT cutoffs may have profound public health ramifications. We aimed to determine the optimal threshold for 13C-UBT positivity in our population. Methods: Consecutive test samples collected at our central laboratory from patients undergoing a first-time 13C-UBT between 1 January 2010 and 31 December 2015 were included. The difference between values at 30 minutes and at baseline (T30–T0) was expressed as delta over baseline (DOB). Cluster analysis was performed on the 13C-UBT test results to determine the optimal cutoff point with minimal interclass variance. Results: Two lakhs thirty four thousand eight hundred thirty one patients (87 291 (37.2%) male, age 39.9 ± 19.9) underwent a first-time 13C-UBT, including 124 701 (53.1%) negative and 110 130 (46.9%) positive tests, using the manufacturer-recommended cutoff of 3.5 DOB. Cluster analysis determined an optimized cutoff of 2.74 DOB, representing an additional 2180 (0.93%) positive subjects who had been previously categorized as negative according to the manufacturer-specified cutoff of 3.5 DOB. Mean positive and negative DOB values were 19.54 ± 14.95 and 0.66 ± 0.51, respectively. The cutoffs for male and female subjects were 2.23 and 3.05 DOB, respectively. Threshold values for <45-year-olds, 45-60-year-olds and >60-year-olds were 2.67, 2.55, and 2.93 DOB, respectively. Of the 2180 (0.93%) patients with DOB 2.73-3.49, 289 (13.3%) performed a subsequent 13C-UBT and 140 (48.4%) remained positive when tested at 20.3 ± 14.4 months. Conclusions: Major referral laboratories should optimize threshold values for 13C-UBT positivity for their geographical location. Different cutoff values should be applied for male and female subjects.