Table 1 Characteristics of rheumatoid arthritis (RA) index cases

Females (n (%))

375 (86%)

Mean age at disease onset (years) (± standard deviation)

31.1 (9.7)

Mean disease duration (years) (± standard deviation)

9.8(8.5)

With bone erosions (n (%))

336 (77%)

Seropositive for rheumatoid factor (n (%))

323 (76%) (out of 425 RA patients)

Seropositive for anti-cycle citrullinated peptides antibodies (n (%))

214 (76%) (out of 282 RA patients)

Carrying at least one HLA-DRB1 shared epitope allele (n (%))^a

152 (77%) (out of 197 RA patients)

Carrying at least one PTPN22-1858T allele (n (%))

115 (27%)

Carrying the TRAF1/C5 rs10818488-A variant (n (%))

277 (64%)