Table 1.

Characteristics of rheumatoid arthritis (RA) index cases from the investigated samples

	TDT RA sample 1 (n = 100)	TDT RA sample 2 (n = 100)	ASP RA sample (n = 88)
Female (%)	87	90	84
Mean age (± standard deviation) at disease onset (years)	32 (± 10)	31 (± 6)	40 (± 14)
Mean (± standard deviation) disease duration (years)	18 (± 7)	16 (± 8)	23 (± 10)
RA patients with bone erosions (%)	90	79	80
RA patients seropositive for rheumatoid factor (%)	81	76	84
RA patients carrying at least one HLA-DRB1 shared epitope allelea (%)	78	80	77

TDT, transmission disequilibrium test; ASP, affected sib-pair

^aDRB1*0101, DRB1*0102, DRB1*0401, DRB1*0404, DRB1*0405, DRB1*0408, DRB1*1001.