Table 4.

IRR for vessel stenosis in SWiTCH subjects with either low or uninterpretable TCD velocities compared with normal TCD velocities

Vasculopathy region	TCD result	IRR (95% CI)	P value
ACA	Low	1.2 (1.0, 1.5)	.073
	Uninterpretable	1.3 (1.1, 1.6)	.004
DICA	Low	1.9 (1.2, 3.1)	.006
	Uninterpretable	1.9 (1.4, 2.5)	<.0001
MCA	Low	5.1 (3.1, 8.3)	<.0001
	Uninterpretable	4.1 (2.7, 6.4)	<.0001
PCA	Low	2.8 (1.1, 6.9)	.031
	Uninterpretable	1.8 (0.7, 4.6)	.227

Risk ratios were determined using a Poisson model controlling for age at index stroke, previous history of TIA, and hemisphere.