title: Validating inflammatory bowel disease (IBD) in the Swedish National Patient Register and the Swedish Quality Register for IBD (SWIBREG).
abstract: BACKGROUND
  Both the Swedish National Patient Register (NPR) and the Swedish Quality Register for inflammatory bowel disease (IBD, SWIBREG) are important sources of research data and information. However, the validity of a diagnosis of IBD in these registers is unknown.
  
  
  METHODS
  Medical charts of 129 randomly selected patients from the NPR and 165 patients registered both in SWIBREG and the NPR were reviewed. Patients were classified according to standardized criteria for ulcerative colitis (UC), Crohn's disease (CD), or IBD unclassified (IBD-U). Positive predictive values (PPVs) for UC, CD, IBD-U (only SWIBREG), or having any form of IBD were then calculated.
  
  
  RESULTS
  For cases with ≥2 diagnoses of IBD in the NPR (hospitalizations or non-primary care outpatient visits), the PPV was 93% (95% CI: 87-97) for any IBD, 79% (66-88) for UC and 72% (60-82) for CD. In UC patients with ≥2 UC diagnoses but never a CD diagnosis, the PPV increased to 90% (77-97). The PPV for CD in patients with ≥2 CD diagnoses but never a UC diagnosis was 81% (67-91)). Combining data from SWIBREG (≥1 record) and the NPR (≥1 record), the PPV was 99% for any IBD (97-100), 96% (89-99) for UC, and 90% (82-96) for CD.
  
  
  CONCLUSIONS
  The validity of the UC, CD, and IBD diagnoses is high in the NPR but even higher when cases were identified both in SWIBREG and the NPR. These results underline the need for a well-functioning Swedish Quality Register for IBD as a complement to the NPR.
authors: a Department of Medical Epidemiology and Biostatistics , Karolinska Institutet , Stockholm , Sweden.
authors: Gustav L
authors: GL
authors: Jakobsson
authors: a Department of Medical Epidemiology and Biostatistics , Karolinska Institutet , Stockholm , Sweden.
authors: Emil
authors: E
authors: Sternegård
authors: b Department of Pediatric Gastroenterology , Sachs' Children's Hospital , Stockholm , Sweden.|c Clinical Epidemiology Unit, Department of Medicine Solna , Karolinska Institutet , Stockholm , Sweden.
authors: Ola
authors: O
authors: Olén
authors: d Department of Clinical and Experimental Medicine , Linköping University , Linköping , Sweden.|e Department of Surgery , Linköping University Hospital , Linköping , Sweden.
authors: Pär
authors: P
authors: Myrelid
authors: f Institute of Environmental Medicine, Karolinska Institutet , Stockholm , Sweden.
authors: Rickard
authors: R
authors: Ljung
authors: g Department of Internal Medicine , Södra Älvsborgs sjukhus , Borås , Sweden.|h Institute of Medicine , Sahlgrenska Academy , University of Gothenburg, Gothenburg , Sweden.
authors: Hans
authors: H
authors: Strid
authors: i Department of Gastroenterology, Faculty of Medicine and Health , Örebro University , Örebro , Sweden.
authors: Jonas
authors: J
authors: Halfvarson
authors: a Department of Medical Epidemiology and Biostatistics , Karolinska Institutet , Stockholm , Sweden.|j Department of Pediatrics , Örebro University Hospital , Örebro , Sweden.|k Division of Epidemiology and Public Health, School of Medicine , University of Nottingham , Nottingham , UK.|l Department of Medicine , Columbia University College of Physicians and Surgeons , New York , NY , USA.
authors: Jonas F
authors: JF
authors: Ludvigsson
mesh_terms: D016099:Endoscopy, Gastrointestinal; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000145:classification* / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging; D012042:Registries; D013548:Sweden; D014057:Tomography, X-Ray Computed
keywords: Inflammatory bowel disease; National Patient Register; validation