title: Methodological Challenges When Comparing Demographic and Clinical Characteristics of International Observational Registries.
abstract: OBJECTIVE
  Comparisons of data from different registries can be helpful in understanding variations in many aspects of rheumatoid arthritis (RA). The study aim was to assess and improve the comparability of demographic, clinical, and comorbidity data from 5 international RA registries.
  
  
  METHODS
  Using predefined definitions, 2 subsets of patients (main cohort and subcohort) from 5 international observational registries (Consortium of Rheumatology Researchers of North America Registry [CORRONA], the Swedish Rheumatology Quality of Care Register [SRR], the Norfolk Arthritis Register [NOAR], the Institute of Rheumatology Rheumatoid Arthritis cohort [IORRA], and CORRONA International) were evaluated and compared. Patients ages >18 years with RA, and present in or recruited to the registry from January 1, 2000, were included in the main cohort. Patients from the main cohort with positive rheumatoid factor and/or erosive RA who had received ≥1 synthetic disease-modifying antirheumatic drug (DMARD), and switched to or added another DMARD, were included in the subcohort at time of treatment switch.
  
  
  RESULTS
  Age and sex distributions were fairly similar across the registries. The percentage of patients with a high Disease Activity Score in 28 joints score varied between main cohorts (17.5% IORRA, 18.9% CORRONA, 24.7% NOAR, 27.7% CORRONA International, and 36.8% SRR), with IORRA, CORRONA, and CORRONA International including more prevalent cases of RA; the differences were smaller for the subcohort. Prevalence of comorbidities varied across registries (e.g., coronary artery disease ranged from 1.5% in IORRA to 7.9% in SRR), partly due to the way comorbidity data were captured and general cultural differences; the pattern was similar for the subcohorts.
  
  
  CONCLUSIONS
  Despite different inclusion criteria for the individual RA registries, it is possible to improve the comparability and interpretability of differences across RA registries by applying well-defined cohort definitions.
authors.affiliation: University of Manchester, Manchester, UK.
authors.forename: Suzanne M M
authors.initials: SM
authors.lastname: Verstappen
authors.affiliation: Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Askling
authors.affiliation: AstraZeneca, MöIndal, Sweden.
authors.forename: Niklas
authors.initials: N
authors.lastname: Berglind
authors.affiliation: AstraZeneca, MöIndal, Sweden.
authors.forename: Stefan
authors.initials: S
authors.lastname: Franzen
authors.affiliation: Karolinska Institutet, Stockholm, Sweden.
authors.forename: Thomas
authors.initials: T
authors.lastname: Frisell
authors.affiliation: University of Manchester, Manchester, UK.
authors.forename: Christopher
authors.initials: C
authors.lastname: Garwood
authors.affiliation: New York University School of Medicine, New York, and CORRONA, Southborough, Massachusetts.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Greenberg
authors.affiliation: Karolinska Institutet, Stockholm, Sweden.
authors.forename: Marie
authors.initials: M
authors.lastname: Holmqvist
authors.affiliation: AstraZeneca, Wilmington, Delaware.
authors.forename: Laura
authors.initials: L
authors.lastname: Horne
authors.affiliation: AstraZeneca, Wilmington, Delaware.
authors.forename: Kathy
authors.initials: K
authors.lastname: Lampl
authors.affiliation: University of Nebraska Medical Center, Omaha, and the National Data Bank for Rheumatic Diseases, Wichita, Kansas.
authors.forename: Kaleb
authors.initials: K
authors.lastname: Michaud
authors.affiliation: AstraZeneca, MöIndal, Sweden, and University of Gothenburg, Gothenburg, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Nyberg
authors.affiliation: Columbia University College of Physicians and Surgeons, New York, New York.
authors.forename: Dimitrios A
authors.initials: DA
authors.lastname: Pappas
authors.affiliation: University of Massachusetts Medical School, Worcester.
authors.forename: George
authors.initials: G
authors.lastname: Reed
authors.affiliation: Manchester Academic Health Science Centre, Central Manchester NHS Foundation Trust, and University of Manchester, Manchester, UK.
authors.forename: Deborah P M
authors.initials: DP
authors.lastname: Symmons
authors.affiliation: Institute of Rheumatology, Tokyo Women's Medical University, Tokyo, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Tanaka
authors.affiliation: MedImmune, Gaithersburg, Maryland.
authors.forename: Trung N
authors.initials: TN
authors.lastname: Tran
authors.affiliation: Institute of Rheumatology, Tokyo Women's Medical University, Tokyo, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yamanaka
authors.affiliation: AstraZeneca, Macclesfield, UK.
authors.forename: Meilien
authors.initials: M
authors.lastname: Ho
mesh_terms: D017677:Age Distribution; D000368:Aged; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology / Q000628:therapy; D001208:Asia / Q000453:epidemiology; D015415:Biomarkers / Q000097:blood; D015897:Comorbidity; D057915:Drug Substitution; D004359:Drug Therapy, Combination; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009656:North America / Q000453:epidemiology; D015995:Prevalence; D012042:Registries / Q000592:standards*; D012107:Research Design / Q000592:standards*; D012217:Rheumatoid Factor / Q000097:blood; D017678:Sex Distribution; D013020:South America / Q000453:epidemiology; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D018501:Antirheumatic Agents; D015415:Biomarkers; D012217:Rheumatoid Factor