The reliability of the ankle-brachial index in the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS)

Table 3 Variation in DINAMAP™ measurements of the ankle-brachial index by subgroup defined at the first measurement

		Square root of variance components
Subgroup	N	Between-person	Within-person	Total	Reliability Coefficient	Within-person CV, %
Overall	119	0.133	0.106	0.170	0.612	9.0
Age, y
≤ 62	66	0.124	0.104	0.162	0.587	8.9
> 62	53	0.144	0.107	0.180	0.643	9.1
Race/ethnicity
African American^†	19	0.098	0.079	0.125	0.606	6.8
White	100	0.139	0.110	0.177	0.614	9.3
Gender
Male	49	0.140	0.102	0.173	0.653	8.4
Female	70	0.122	0.109	0.163	0.555	9.5
Field center
Forsyth County, NC	77	0.127	0.116*	0.172	0.545	9.9*
Minneapolis, Minn	42	0.142	0.086*	0.166	0.732	7.2*
Body mass index, kg/m²
≤ 27	61	0.141	0.083*	0.164	0.741*	7.1*
> 27	58	0.124	0.126*	0.178	0.495*	10.7*
Diabetes
No	106	0.134	0.099	0.167	0.646	8.4
Yes^†	13	0.112	0.150	0.187	0.358	13.3
Hypertension
No	76	0.128	0.100	0.163	0.622	8.3
Yes	43	0.134	0.116	0.177	0.574	10.1
Hypertension rx switch^‡
No	101	0.136	0.104	0.171	0.630	8.8
Yes^†	18	0.114	0.115	0.162	0.498	9.9
Coronary heart disease
No	88	0.129	0.098	0.162	0.638	8.3
Yes	31	0.148	0.116	0.188	0.619	9.9
Legs
Same	51	0.115	0.118	0.165	0.486*	10.0
Different	68	0.146	0.094	0.174	0.706*	8.6
Days between measures
≤ 240	60	0.131	0.107	0.169	0.602	9.1
> 240	59	0.136	0.103	0.171	0.633	8.7
FHS sampling group
African American^†	19	0.098	0.079	0.125	0.606	6.8
High family risk score	68	0.148	0.114	0.187*	0.629	9.7
Random sample	32	0.117	0.099	0.153*	0.581	8.2

*p < 0.05 for the difference between the two subgroups (the 95% bootstrapped confidence interval for the difference did not include zero).
^†Proportion too small to perform statistical tests of differences.
^‡"No" includes those who were either taking or not taking hypertension medication at the time of both ABI measures; "yes" includes those who were taking hypertension medication at the time of one ABI measure and not taking hypertension medication at the time of the other ABI measure.

ISSN: 1471-2261