Toe-brachial index and toe systolic blood pressure for the diagnosis of peripheral arterial disease

Abstract

Background Peripheral arterial disease (PAD) of the lower limbs is caused by atherosclerotic occlusive disease in which narrowing of arteries reduces blood flow to the lower limbs. PAD is common; it is estimated to affect 236 million individuals worldwide. Advanced age, smoking, hypertension, diabetes and concomitant cardiovascular disease are common factors associated with increased risk of PAD. Complications of PAD can include claudication pain, rest pain, wounds, gangrene, amputation and increased cardiovascular morbidity and mortality. It is therefore clinically important to use diagnostic tests that accurately identify PAD. Accurate and timely detection of PAD allows clinicians to implement appropriate risk management strategies to prevent complications, slow progression or intervene when indicated. Toe‐brachial index (TBI) and toe systolic blood pressure (TSBP) are amongst a suite of non‐invasive bedside tests used to detect PAD. Both TBI and TSBP are commonly utilised by a variety of clinicians in different settings, therefore a systematic review and meta‐analysis of their diagnostic accuracy is warranted and highly relevant to inform clinical practice. Objectives To (1) estimate the accuracy of TSBP and TBI for the diagnosis of PAD in the lower extremities at different cut‐off values for test positivity in populations at risk of PAD, and (2) compare the accuracy of TBI and TSBP for the diagnosis of PAD in the lower extremities. Secondary objectives were to investigate several possible sources of heterogeneity in test accuracy, including the following: patient group tested (people with type 1 or type 2 diabetes, people with renal disease and general population), type of equipment used, positivity threshold and type of reference standard. Search methods The Cochrane Vascular Information Specialist searched the MEDLINE, Embase, CINAHL, Web of Science, LILACS, Zetoc and DARE databases and the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 27 February 2024. Selection criteria We included diagnostic case‐control, cross‐sectional, prospective and retrospective studies in which all participants had either a TSBP or TBI measurement plus a validated method of vascular diagnostic imaging for PAD. We needed to be able to cross‐tabulate (2 x 2 table) results of the index test and the reference standard to include a study. To be included, study populations had to be adults aged 18 years and over. We included studies of symptomatic and asymptomatic participants. Studies had to use TSBP and TBI (also called toe‐brachial pressure index (TBPI)), either individually, or in addition to other non‐invasive tests as index tests to diagnose PAD in individuals with suspected disease. We included data collected by photoplethysmography, laser Doppler, continuous wave Doppler, sphygmomanometers (both manual and aneroid) and manu...