Table 3.

SIRs calculated for concordant and discordant associations in siblings—Sweden, 1973–2004

	AS			SLE			RA
Subtype	O	SIR	95% CI	O	SIR	95% CI	O	SIR	95% CI
AS	102	17.14	9.88, 29.44	3	0.79	0.11, 3.30	40	1.67	0.85, 3.23
SLE	3	0.80	0.11, 3.37	43	17.02	8.71, 32.45	37	2.39	1.19, 4.67
RA	38	1.74	0.87, 3.39	33	2.32	1.13, 4.61	515	5.12	3.31, 7.89
All	143	4.54	2.71, 7.57	79	3.84	2.15, 6.77	592	4.23	2.76, 6.49

Bold type: 95% CI does not include 1.00. O: observed number of sibling cases.