Table 1

RA study populations from six Northwestern European countries included in the present study*

SwedenDenmarkIcelandNorwayUK biobankFinnGen
RA overall31 313995 37786589418766286 9643613341 78888128 5175798402 7674701125 923
Seropositive RA18 019991 60464559423485086 9641746313 70458728 517913407 6523468145 344
Seronegative RA85151 015 47118529436265286 9661069322 80845528 5171051407 5141436143 312
Serology lacking4779351160798038340
  • *The following ICD-10 codes were used, in addition to clinical diagnoses validated by physicians, from case–control studies on RA or Scandinavian rheumatology quality and patient registers: RA overall (M05.8, M05.9, M06.0, M06.8, M06.9), seropositive RA (M05.8, M05.9 and/or positive rheumatoid factor (RF) and/or anti-CCP antibody measurement), seronegative RA (M06.0, M06.8 or M06.9 with negative RF measurement (and negative anti-CCP measurement if available). See Methods for further details.

  • Ca, number of cases; Co, number of controls; RA, rheumatoid arthritis.