Simple ABI measurement may improve CV risk prediction. Source: Vascular Web

An ankle brachial index measurement may improve the accuracy of cardiovascular risk prediction beyond the Framingham risk score, according to a study in the July 9 issue of the Journal of the American Medical Association.

Gerry Fowkes, PhD, from the Wolfson Unit for Prevention of Peripheral Vascular Diseases, at the University of Edinburgh in Scotland, and colleagues sought to determine if the ankle brachial index (ABI) provides information on the risk of cardiovascular events and mortality independently of the Framingham risk score (FRS) and whether it can improve risk prediction.

The researchers searched MEDLINE from 1950 to February 2008 and EMBASE from 1980 to February 2008, for studies in which participants were derived from a general population, ABI was measured at baseline, and individuals were followed up to detect total and cardiovascular mortality. They included 16 population cohort studies fulfilling the inclusion criteria.

The investigators extracted pre-specified data on individuals in each selected study into a combined data set and conducted an individual participant data meta-analysis was on individuals, who had no previous history of coronary heart disease.

During the follow-up of 24,955 men and 23,339 women, the authors wrote that the risk of death by ABI had a reverse J-shaped distribution with a normal ABI of 1.11 to 140.

Fowkes and colleagues found that the 10-year cardiovascular mortality in men with a low ABI (≤0.90) was 18.7 percent and with normal ABI (1.11-1.40) was 4.4 percent, while corresponding mortalities in women were 12.6 percent and 4.1 percent.

The researchers found that a low ABI (≤0.90) was associated with approximately twice the 10-year total mortality, cardiovascular mortality and major coronary event rate compared with the overall rate in each FRS category.

The authors wrote that the inclusion of the ABI in cardiovascular risk stratification using the FRS would result in reclassification of the risk category and modification of treatment recommendations in approximately 19 percent of men and 36 percent of women.

Based on their results, Fowkes and colleagues concluded that when using the FRS, also measuring with ABI is “justified to improve prediction of cardiovascular risk and provision of advice on ways to reduce that risk. A new risk equation incorporating the ABI and relevant Framingham risk variables could more accurately predict risk and our intention is to develop and validate such a model in our combined data set.”