title: Occult H. pylori infection partially explains 'false-positive' results of (13)C-urea breath test.
abstract: BACKGROUND
  In a previous study, UBiT-100 mg, (Otsuka, Spain), a commercial (13)C-urea breath test omitting citric acid pre-treatment, 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 = 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.
authors.affiliation: Digestive Diseases Department, Corporació Sanitària i Universitària Parc Taulí, Sabadell, Spain ; Departament de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain ; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Instituto de Salud Carlos III, Barcelona, Spain.
authors.forename: María J
authors.initials: MJ
authors.lastname: Ramírez-Lázaro
authors.affiliation: Digestive Diseases Department, Corporació Sanitària i Universitària Parc Taulí, Sabadell, Spain ; Departament de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain ; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Instituto de Salud Carlos III, Barcelona, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: Lario
authors.affiliation: Digestive Diseases Department, Corporació Sanitària i Universitària Parc Taulí, Sabadell, Spain ; Departament de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain ; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Instituto de Salud Carlos III, Barcelona, Spain.
authors.forename: Xavier
authors.initials: X
authors.lastname: Calvet
authors.affiliation: Digestive Diseases Department, Corporació Sanitària i Universitària Parc Taulí, Sabadell, Spain ; Departament de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain ; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Instituto de Salud Carlos III, Barcelona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Sánchez-Delgado
authors.affiliation: Digestive Diseases Department, Corporació Sanitària i Universitària Parc Taulí, Sabadell, Spain ; Departament de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain ; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Instituto de Salud Carlos III, Barcelona, Spain.
authors.forename: Antònia
authors.initials: A
authors.lastname: Montserrat
authors.affiliation: Digestive Diseases Department, Corporació Sanitària i Universitària Parc Taulí, Sabadell, Spain ; Departament de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain.
authors.forename: Elisa M
authors.initials: EM
authors.lastname: Quílez
authors.affiliation: Pathology Department, UDIAT-CD, Corporació Sanitària i Universitària Parc Taulí, Sabadell, Spain.
authors.forename: Alex
authors.initials: A
authors.lastname: Casalots
authors.affiliation: Epidemiology and Evaluation Unit, Fundació Parc Taulí- UAB, Sabadell, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Suarez
authors.affiliation: Digestive Diseases Department, Corporació Sanitària i Universitària Parc Taulí, Sabadell, Spain ; Departament de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain ; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Instituto de Salud Carlos III, Barcelona, Spain.
authors.forename: Rafel
authors.initials: R
authors.lastname: Campo
authors.affiliation: Digestive Diseases Department, Corporació Sanitària i Universitària Parc Taulí, Sabadell, Spain ; Departament de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain ; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Instituto de Salud Carlos III, Barcelona, Spain.
authors.forename: Enric
authors.initials: E
authors.lastname: Brullet
authors.affiliation: Digestive Diseases Department, Corporació Sanitària i Universitària Parc Taulí, Sabadell, Spain ; Departament de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain ; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Instituto de Salud Carlos III, Barcelona, Spain.
authors.forename: Félix
authors.initials: F
authors.lastname: Junquera
authors.affiliation: Microbiology Laboratory, UDIAT-CD, Corporació Sanitària i Universitaria Parc Taulí, Sabadell, Spain ; Spanish Network for the Research in Infectious Diseases (REIPI RD06/0018), Sevilla, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Sanfeliu
authors.affiliation: Departament de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain ; Spanish Network for the Research in Infectious Diseases (REIPI RD06/0018), Sevilla, Spain ; Infectious Diseases Department, Corporació Sanitària i Universitària Parc Taulí, Sabadell, Spain.
authors.forename: Ferran
authors.initials: F
authors.lastname: Segura
keywords: Bacterial infection; Helicobacter pylori; diagnostic tests; false positive results; sensitivity; specificity; urea breath tests