OPTIMIZATION OF C13-UREA BREATH TEST THRESHOLD LEVELS FOR THE DETECTION OF HELICOBACTER PYLORI INFECTION IN A NATIONAL REFERRAL LABORATORY

Tsachi Tsadok Perets 1,2 Rachel Gingold-Belfer 1,3 Zohar Levi 1,3 Ram Dickman 1,3 Doron Boltin 1,3
1Sackler School of Medicine, Tel Aviv Univeristy, Tel Aviv, Israel
2Rabin Medical Center, Gastroenterology Laboratory, Petah Tikva, Israel
3Rabin Medical Center, Gastroenterology Division, Petah Tikva, Israel

Background: Threshold values for C13-urea breath test (C13-UBT) positivity may be affected by sociodemographic factors, host factors such as C13 excretion kinetics, bacterial factors and laboratory factors including urea dose. Manufacturer recommended cutoffs for C13-UBT assays may not be applicable in all settings. Optimizing C13-UBT cut-offs may have profound public health ramifications. We aimed to determine the optimal threshold for C13-UBT positivity in our population.

Methods: Consecutive test samples collected at our central laboratory from patients undergoing a first-time C13-UBT between 1st January 2010 and 31st December 2015 were included. The difference between values at 30 min and at baseline (T30–T0) was expressed as delta over baseline (DOB). Cluster analysis was performed on the C13-UBT test results to determine the optimal cut-off point with minimal interclass variance.

Results: 234,831 patients (87,291 (37.2%) male, age 39.9±19.9) underwent a first-time C13-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 cut-off 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 cut-offs 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 C13-UBT and 140 (48.4%) remained positive when tested at 20.3±14.4 months.

Conclusions: Major referral laboratories should optimize threshold values for C13-UBT positivity for their geographical location. Different cut-off values should be applied for male and female subjects.









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