Table 1.

Clinical characteristics of North American Native patients with rheumatoid arthritis (RA) and Native controls. Results are reported as percentage positive, mean (SD), or median (interquartile range; IQR) as indicated. All comparisons between RA and controls, p < 0.0001.

Characteristic	RA, n = 448	Controls, n = 704
Sex, % female	82	59
Age, yrs	47 (15)	35 (12)
RF-positive, %	86	32
RF titer, median (IQR)	171 (400)	19 (3)
ACPA-positive^*, %	73	2.8
Shared epitope^†, %	85	66

↵* Anticitrullinated protein antibody (ACPA) tested in 252 patients with RA, 529 controls.
↵† One or more copies of shared-epitope (HLA-DRB1 alleles 0101, 0102, 0401, 0404, 0405, 0408, 0410, 1001, 1402) tested in 348 patients with RA and 330 controls. RF: rheumatoid factor.