Table 2

Characteristics of data sources used for identification of RA patients included in the epidemiological analysis

Data typeAdministrative data on physician visits, hospitalisations and medicationsPatient questionnaireElectronic medical recordsPatient questionnaire and assessmentElectronic medical records, patient assessment
Time period1996–20011998–20031987–20011990–91994–2003
No of RA patients in cohort27 71021 22938 6228393703
Type of cohortPopulation-based, prevalent casesLongitudinal cohort, prevalent cases referred by rheumatologistsPopulation-based, prevalent casesEarly RA cohortEarly RA cohort
No of DMARD-treated RA patients12 33710 49914 4675233703
DMARD usersPrevalent usersPrevalent usersPrevalent usersIncident usersIncident users
Case ascertainmentICD-9 codes on claims and discharge summariesPatient-reported and verified by medical and hospital recordsOXMIS codes; codes validated by an oncologistICD-9 codes in linked medical recordsICD-10 codes and verified by linking to cancer registry
  • BC, British Columbia RA Cohort; DMARD, disease-modifying antirheumatic drug; GPRD, General Practice Research Database; ICD, International Classification of Diseases; NDB, National Data Bank for Rheumatic Diseases; NOAR, Norfolk Arthritis Register; RA, rheumatoid arthritis; Sweden ERA, Sweden Early Rheumatoid Arthritis Register.