Abstract 4201: Ankle Brachial Index Improves Prediction of Mortality Determined by Framingham Risk Score in 48,115 Healthy Subjects in Sixteen Studies Worldwide.
Both low ankle brachial index (ABI) and high Framingham Risk Score (FRS) are each associated with an increased risk of death. The aims of our study were
to determine for the first time how the ABI might improve prediction determined by the FRS and
definitively ascertain the normal and at risk levels of the ABI to be used in clinical practice. The study was an individual patient meta-analysis of data from 16 major population cohort studies based in the USA, Europe and Australia and participating in the ABI Collaboration. 24885 men and 23230 women, who had no history of cardiovascular disease and who had an ABI measured at baseline, were included. From a low (≤ 0.6) to a high (>1.4) ABI the risk of death followed a reversed J shaped (ski jump) curve which indicated that the ABI might be categorised usefully in both men and women as ≤ 0.9 (low abnormal), 0.91–1.1 (slightly abnormal), 1.11–1.4 (normal) and > 1.4 (high abnormal). The pooled relative hazard for death for those with a low abnormal compared to normal ABI was 3.23 (95% CI 2.99 to 3.48) for men and 2.79 (95% CI 2.55 to 3.03) for women. For those in the bottom quintile of FRS the 10 year all cause mortality was 8% for men and 9% for women rising to 35% for men and 18% for women in the top quintile. Inclusion of the ABI resulted in those with an ABI of ≤ 0.9 doubling their absolute mortality risk at every FRS level. In those with an ABI > 1.4 a slight increase in mortality was found. Use of the ABI would result in almost 10% of the population having a reclassification of their mortality risk. Similar results were found for cardiovascular mortality. These findings indicate that the ABI has potential to be included as a screening tool for cardiovascular and all cause mortality in the healthy population but further work is required to determine if there are specific groups, for example the elderly, in which use of the ABI is most beneficial.