Prevalence and risk factors of PAD among patients with elevated ABI.

OBJECTIVES: To assess the prevalence and clinical significance of elevated ankle-brachial index (ABI) in patients referred to vascular consultation.

DESIGN: Retrospective clinical study.

MATERIAL AND METHODS: In 1,762 patients referred with a suspicion of peripheral arterial disease (PAD), ABI and toe brachial index (TBI) were measured by photoplethysmography. ABI>/=1.3 was considered falsely elevated and TBI<0.60 was the diagnostic criterion for PAD.

RESULTS: The prevalence of elevated ABI was 8.4% and that of PAD among these patients 62.2%. PAD was significantly more prevalent among subjects with severe symptoms (rest pain, ulcers or gangrene) than in those with intermittent claudication (83.8% and 45.3%, respectively, p<0.001). The risk of PAD diagnosis was ten-fold (OR 10.31, 95% CI 2.07-51.30) among those with chronic renal failure, five-fold among patients with a history of smoking (OR 5.63, 95% CI 1.22-26.00) and over three-fold (OR 3.44, 95% CI 1.46-8.12) among those with coronary heart disease. The specificities of elevated ABI threshold levels (1.3, 1.4 and 1.5) in identifying PAD were 86%, 94% and 96%, respectively, the sensitivities being 44%, 38% and 36%, respectively.

CONCLUSIONS: The prevalence of elevated ABI in patients referred to vascular consultation is 8.4% and that of PAD among these 62.2%. PAD is significantly more probable among those with chronic renal failure, a history of smoking and coronary heart disease. Furthermore, the specificity of elevated ABI (>/=1.3) in recognizing PAD is good, whereas the sensitivity is only satisfactory.