title: Smelling the Diagnosis: The Electronic Nose as Diagnostic Tool in Inflammatory Arthritis. A Case-Reference Study.
abstract: OBJECTIVE
  To investigate whether exhaled breath analysis using an electronic nose can identify differences between inflammatory joint diseases and healthy controls.
  
  
  METHODS
  In a cross-sectional study, the exhaled breath of 21 rheumatoid arthritis (RA) and 18 psoriatic arthritis (PsA) patients with active disease was compared to 21 healthy controls using an electronic nose (Cyranose 320; Smiths Detection, Pasadena, CA, USA). Breathprints were analyzed with principal component analysis, discriminant analysis, and area under curve (AUC) of receiver operating characteristics (ROC) curves. Volatile organic compounds (VOCs) were identified by gas chromatography and mass spectrometry (GC-MS), and relationships between breathprints and markers of disease activity were explored.
  
  
  RESULTS
  Breathprints of RA patients could be distinguished from controls with an accuracy of 71% (AUC 0.75, 95% CI 0.60-0.90, sensitivity 76%, specificity 67%). Breathprints from PsA patients were separated from controls with 69% accuracy (AUC 0.77, 95% CI 0.61-0.92, sensitivity 72%, specificity 71%). Distinction between exhaled breath of RA and PsA patients exhibited an accuracy of 69% (AUC 0.72, 95% CI 0.55-0.89, sensitivity 71%, specificity 72%). There was a positive correlation in RA patients of exhaled breathprints with disease activity score (DAS28) and number of painful joints. GC-MS identified seven key VOCs that significantly differed between the groups.
  
  
  CONCLUSIONS
  Exhaled breath analysis by an electronic nose may play a role in differential diagnosis of inflammatory joint diseases. Data from this study warrant external validation.
authors.affiliation: Division of Clinical Immunology and Rheumatology, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Marjolein P
authors.initials: MP
authors.lastname: Brekelmans
authors.affiliation: Department of Respiratory Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Niki
authors.initials: N
authors.lastname: Fens
authors.affiliation: Department of Respiratory Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Paul
authors.initials: P
authors.lastname: Brinkman
authors.affiliation: Department of Respiratory Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.|Department of Intensive Care Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Lieuwe D
authors.initials: LD
authors.lastname: Bos
authors.affiliation: Department of Respiratory Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Sterk
authors.affiliation: Division of Clinical Immunology and Rheumatology, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Paul P
authors.initials: PP
authors.lastname: Tak
authors.affiliation: Division of Clinical Immunology and Rheumatology, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Daniëlle M
authors.initials: DM
authors.lastname: Gerlag
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000175:diagnosis*; D001944:Breath Tests; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D062609:Electronic Nose; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008297:Male; D008875:Middle Aged; D055549:Volatile Organic Compounds / Q000032:analysis*; D055815:Young Adult
chemical_list: D055549:Volatile Organic Compounds