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​Occult H. Pylori Infection Partially Explains False Positive Results Of 13C Urea Breath Test

Occult H. pylori infection partially explains ‘false-positive’ results of 13C-urea breath test 


Marı´a J Ramı´rez-La´zaro1,2,3, Sergio Lario1,2,3, Xavier Calvet1,2,3, Jordi Sa´nchez-Delgado1,2,3, 

Anto`nia Montserrat1,2,3, Elisa M Quı´lez1,2, Alex Casalots4 , David Suarez5 , Rafel Campo1,2,3, 

Enric Brullet1,2,3, Fe´lix Junquera1,2,3, Isabel Sanfeliu6,7 and Ferran Segura2,7,8 


Abstract 

Background: In a previous study, UBiT-100 mg, (Otsuka, Spain), a commercial 13C-urea 

breath test omitting citric acid pretreatment, had a high rate of false-positive results; 

however, it is possible that UBiT detected low-density ‘occult’ infection missed by 

other routine reference tests. We aimed to validate previous results in a new cohort 

and to rule out the possibility that false-positive UBiT were due to an ‘occult’ 

infection missed by reference tests. 


Methods: Dyspeptic patients (n ¼ 272) were prospectively enrolled and UBiT was performed, 

according to the manufacturer’s recommendations. Helicobacter pylori infection was 

determined by combining culture, histology and rapid urease test results. We calculated 

UBiT sensitivity, specificity, positive and negative predictive values (with 95% CI). 

In addition, we evaluated ‘occult’ H. pylori infection using two previously-validated 

polymerase chain reaction (PCR) methods for urease A (UreA) and 16 S sequences in gastric 

biopsies. We included 44 patients with a false-positive UBiT, and two control groups of 

25 patients each, that were positive and negative for all H. pylori tests. 


Results: UBiT showed a false-positive rate of 17%, with a specificity of 83%. All the positive 

controls and 12 of 44 patients (27%) with false-positive UBiT were positive for all 

two PCR tests; by contrast, none of our negative controls had two positive PCR tests. 


Conclusions: UBiT suffers from a high rate of false-positive results and sub-optimal 

specificity, and the protocol skipping citric acid pre-treatment should be revised; 

however, low-density ‘occult’ H. pylori infection that was undetectable by conventional 

tests accounted for around 25% of the ‘false-positive’ results. 


Keywords Bacterial infection, diagnostic tests, false positive results, Helicobacter pylori, 

sensitivity, specificity, urea breath tests 


Received: 18 November 2014; accepted: 20 January 2015

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