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Multicenter Study
. 2014 Mar;21(3):310-20.
doi: 10.1177/2047487313516564. Epub 2013 Dec 23.

Development and validation of an ankle brachial index risk model for the prediction of cardiovascular events

F G R Fowkes  1 , G D Murray, I Butcher, A R Folsom, A T Hirsch, D J Couper, G Debacker, M Kornitzer, A B Newman, K C Sutton-Tyrrell, M Cushman, A J Lee, J F Price, R B D'Agostino Sr, J M Murabito, Pe Norman, K H Masaki, L M Bouter, R J Heine, C D A Stehouwer, M M McDermott, H E J H Stoffers, J A Knottnerus, M Ogren, B Hedblad, W Koenig, C Meisinger, J A Cauley, Oh Franco, M G M Hunink, A Hofman, J C Witteman, M H Criqui, R D Langer, W R Hiatt, R F Hamman; Ankle Brachial Index Collaboration
Affiliations
Multicenter Study

Development and validation of an ankle brachial index risk model for the prediction of cardiovascular events

F G R Fowkes et al. Eur J Prev Cardiol. 2014 Mar.

Abstract

Background: The ankle brachial index (ABI) is related to risk of cardiovascular events independent of the Framingham risk score (FRS). The aim of this study was to develop and evaluate a risk model for cardiovascular events incorporating the ABI and FRS.

Design: An analysis of participant data from 18 cohorts in which 24,375 men and 20,377 women free of coronary heart disease had ABI measured and were followed up for events.

Methods: Subjects were divided into a development and internal validation dataset and an external validation dataset. Two models, comprising FRS and FRS + ABI, were fitted for the primary outcome of major coronary events.

Results: In predicting events in the external validation dataset, C-index for the FRS was 0.672 (95% CI 0.599 to 0.737) in men and 0.578 (95% CI 0.492 to 0.661) in women. The FRS + ABI led to a small increase in C-index in men to 0.685 (95% CI 0.612 to 0.749) and large increase in women to 0.690 (95% CI 0.605 to 0.764) with net reclassification improvement (NRI) of 4.3% (95% CI 0.0 to 7.6%, p = 0.050) and 9.6% (95% CI 6.1 to 16.4%, p < 0.001), respectively. Restricting the FRS + ABI model to those with FRS intermediate 10-year risk of 10 to 19% resulted in higher NRI of 15.9% (95% CI 6.1 to 20.6%, p < 0.001) in men and 23.3% (95% CI 13.8 to 62.5%, p = 0.002) in women. However, incorporating ABI in an improved newly fitted risk factor model had a nonsignificant effect: NRI 2.0% (95% CI 2.3 to 4.2%, p = 0.567) in men and 1.1% (95% CI 1.9 to 4.0%, p = 0.483) in women.

Conclusions: An ABI risk model may improve prediction especially in individuals at intermediate risk and when performance of the base risk factor model is modest.

Keywords: Ankle brachial index; cardiovascular diseases; risk assessment.

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Conflict of interest statement

Conflict of interest

The authors declare that there is no conflict of interest.

Figures

Figure 1
Figure 1. Kaplan–Meier 10-year rates in men and women for major coronary events in risk categories predicted by the Framingham risk score with ankle brachial index and the Framingham risk score
Major coronary events are myocardial infarction and death due to coronary heart disease. Kaplan–Meier rates, derived from external validation dataset, are sometimes estimated from small numbers of events and may be imprecise. FRS, Framingham risk score; ABI, ankle brachial index.
See this image and copyright information in PMC

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