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
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