Abstract 2869: Is Ankle Brachial Index a Cost-Effective Screening Tool in Asymptomatic Older Adults?
Background: Previous reports indicate that about 5% of adults aged 40 years or older have an ankle brachial index (ABI) <0.90, an indicator of peripheral vascular disease in the lower extremities (LE). ABI is therefore recommended as a screening tool for cardiovascular disease (CVD), particularly in older adults. The average US cost of performing an ABI is $61.
Objective: The goal of this study is to determine the prevalence of an ABI <0.90 and associated detection costs, in an asymptomatic sample of 1,017 older adults, aged 60–72 years, enrolled in the Atherosclerotic Disease VAscular FunctioN and GenetiC Epidemiology (ADVANCE) study.
Methods: Frequency distributions, sensitivity and specificity, and associated costs of ABI by history of LE circulation problems, CVD risk factors and Framingham risk score (FRS) were calculated.
Results: The prevalence of ABI <0.90 was 2.2%, history of LE circulation problems was 4.4%, while 19.9% had a FRS >20%. Compared to persons with a normal ABI (≥0.90–1.39), persons with an ABI <0.90 were more likely to be smokers (p=0.02), obese (BMI>30, p=0.05), diabetics (p=0.02), physically inactive (p=0.004), have a FRS >20% (p=0.004), and a coronary artery calcium score >10 (p=0.02). ABI >0.90 had a sensitivity of 8.9%, with a specificity of 98.1%, for those reporting LE circulation problems. The positive predictive value of a FRS >20% to detect an ABI <0.90 was 50%. The total estimated cost of using ABI as a screening tool was $62,037. Regardless of FRS, the cost to detect those not reporting LE circulation problems but having an ABI <0.90 was $59,292 ($3294/person). However, for those with a FRS ≤20, not reporting LE circulation problems, the cost to detect those with an ABI <0.90, was $47,458 ($4,746/person).
Conclusions: In asymptomatic older adults, ABI as a screening tool will likely yield only a few positive cases at a relatively large cost. The FRS >20% was no better than chance in positively predicting those with an ABI <0.90. Our data suggest that it may be more cost-effective to utilize a careful history of LE circulation problems and to provide care aimed at CVD risk factor reduction, including physical activity and/or walking counseling for all older adults.