Table 1. RCAα haplotype frequencies in patients with pSS compared with controls.

Haplotype	pSS(2N = 230)	Controls(2N = 196)	OR (95% CI)	p Value
AH1	80 (34.8%)	46 (23.5%)	2.1 (1.3,3.3)*	0.002
AH2	25 (10.9%)	27 (13.8%)	1.3 (0.6,2.1)	0.75
AH3	38 (16.5%)	19 (9.7%)	2.4 (1.3,4.4)	0.006
Other	87 (37.8%)	104 (53.1%)	1
	Global test: χ2 = 14.6, df = 3, p = 0.002

There were three common RCAα block ancestral haplotypes, AH1, AH2 and AH3. “Other” haplotypes, with a frequency between 1 and 3%, were combined for analysis purposes. Both AH1 and AH3 frequencies were increased in patients with pSS relative to controls. This association was attributable to the Ro/La autoantibody-positive subgroup of patients with pSS and was not evident in the minority of patients with pSS who were autoantibody negative (2N = 38).