January 1, 2016Brazilian Journal of Medical and Biological Research16 citationsOpen Access
Different methods of calculating ankle-brachial index in mid-elderly men and women: the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)
Key Result
Calculating the ankle-brachial index using the lowest leg systolic blood pressure (ABI-LOW) identified a higher prevalence of ABI <1.0 (2.7%) compared to the mean (0.9%) or highest (0.5%) readings.
Study Design
Type
Observational (n=13,921)
Structured PICO
Does the method of calculating the ankle-brachial index (highest, mean, or lowest leg systolic pressure) affect cardiovascular risk stratification in adults free of cardiovascular disease?
P
Population
13,921 men and women aged 35 to 74 years free of cardiovascular diseases, evaluated for different methods of calculating the ankle-brachial index.
E
Exposure
Ankle-brachial index calculation using the lowest leg systolic blood pressure reading (ABI-LOW)
C
Comparator
Ankle-brachial index calculation using the highest (ABI-HIGH) or mean (ABI-MEAN) leg systolic blood pressure reading
O
Outcome
Prevalence of ABI < 1.0 and its impact on the 10-year Framingham Risk Score of coronary heart disease >20%surrogate
Calculating the ankle-brachial index using the lowest leg systolic blood pressure (ABI-LOW) identifies more individuals at high cardiovascular risk, making it more suitable for primary prevention purposes.
Main Result
Absolute Event Rate: 2.7% vs 0.5%
Abstract
The ankle-brachial index (ABI) is a marker of subclinical atherosclerosis related to health-adverse outcomes. ABI is inexpensive compared to other indexes, such as coronary calcium score and determination of carotid artery intima-media thickness (IMT). Our objective was to identify how the ABI can be applied to primary care. Three different methods of calculating the ABI were compared among 13,921 men and women aged 35 to 74 years who were free of cardiovascular diseases and enrolled in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). The ABI ratio had the same denominator for the three categories created (the highest value for arm systolic blood pressure), and the numerator was based on the four readings for leg systolic blood pressure: the highest (ABI-HIGH), the mean (ABI-MEAN), and the lowest (ABI-LOW). The cut-off for analysis was ABI20% without the inclusion of ABI<1.0 was 4.9%. For ABI-HIGH, ABI-MEAN and ABI-LOW, the increase in percentage points was 0.3, 0.7, and 2.3%, respectively, and the relative increment was 6.1, 14.3, and 46.9%. In conclusion, all methods were acceptable, but ABI-LOW was more suitable for prevention purposes.