Toe brachial index measured by automated device compared to duplex ultrasonography for detecting peripheral arterial disease in older people

Introduction To investigate the diagnostic accuracy of an automated toe blood pressure device for detecting peripheral arterial disease in older people. Methods Ninety participants underwent toe and brachial blood pressure measurements and colour duplex ultrasonography of the right lower limb. Peripheral arterial disease was diagnosed if > 50% arterial obstruction was identified in any lower limb vessel using colour duplex ultrasonography. A receiver operating characteristic curve was analysed and the sensitivity and specificity of commonly used toe brachial index and toe blood pressure values were determined. Results The optimum toe brachial index threshold value for diagnosing peripheral arterial disease was 0.72 (sensitivity 76.2%, specificity 75%). The area under the curve was 0.829 (95% CI 0.743 to 0.915, p < 0.0001) suggesting fair diagnostic accuracy. A toe blood pressure of 70 mmHg was found to have excellent specificity (97.92%) for detecting PAD but poor sensitivity (42.86%). Conclusions The accuracy of automated toe blood pressure and TBI measurements was determined to be good when using colour duplex ultrasound as the reference standard for the non-invasive diagnosis of peripheral arterial disease. Results should be interpreted in the context of all clinical signs and symptoms.