Automated devices for identifying peripheral arterial disease in people with leg ulceration: an evidence synthesis and cost-effectiveness analysis

Background
Peripheral artery disease is a common condition caused by narrowing/blockage of the arteries, resulting in reduced blood supply. Peripheral artery disease is associated with an increased risk of vascular complications, but early treatment reduces mortality and morbidity. Leg ulcers are long-lasting wounds, usually treated by compression therapy. Compression therapy is not suitable for people with peripheral artery disease, as it can affect the arterial blood supply. In clinical practice, people with peripheral artery disease are identified by measurement of the ankle–brachial pressure index using a sphygmomanometer and manual Doppler device. However, this method can be uncomfortable for people with leg ulcers and automated devices have been proposed as a more acceptable alternative. The objective of this appraisal was to summarise the clinical and cost-effectiveness evidence on the use of automated devices to detect peripheral artery disease in people with leg ulcers.

Methods
 

Clinical effectiveness
To identify reports of relevant studies, we searched major electronic databases and scrutinised the information supplied by the manufacturers of the automated devices under investigation. Due to the lack of evidence on people with leg ulcers, we considered evidence from studies of any design assessing automated devices versus an acceptable reference device in any population receiving ankle–brachial pressure index assessment. We summarised information on diagnostic accuracy of the automated devices and level of agreement with the reference device. For each device, when data permit, we pooled data across studies by conducting random-effects meta-analyses using a Hierarchical Summary Receiving Operating Characteristics model.

Cost-effectiveness
An economic model comprising a decision tree (24 weeks) and Markov models to capture lifetime costs and quality-adjusted life-years associated with venous, arterial and mixed aetiology disease in leg ulcer patients. Analyses were conducted from a United Kingdom National Health Service and Personal Social Services perspective. Costs and quality-adjusted life-years were discounted at 3.5% per year. Deterministic and several probabilistic analyses were used to capture uncertainty surrounding a range of optimistic and pessimistic assumptions about the impact of automated tests on health outcomes (ulcer healing and requirement for invasive management of arterial disease).

Results
 

Clinical effectiveness
From the 116 records retrieved by the electronic searches, we included 24 studies evaluating five devices (BlueDop Vascular Expert, BOSO ABI-System 100, Dopplex Ability, MESI ankle–brachial pressure index MD and WatchBP Office ABI). Two studies assessing people with leg ulcers found that automated devices often gave higher ankle–brachial pressure index readings than manual Doppler (underestimation of arterial disease). In the 22 studies involving people without leg ulcers, automated devices generally demonstrated good specificity and moderate specificity. Meta-analysis of 12 studies showed a pooled sensitivity of 64% (95% confidence interval 57% to 71%) and a pooled specificity of 96% (95% confidence interval 92% to 98%) for detection of peripheral artery disease.

Cost-effectiveness
Automated devices cost less than manual Doppler to deliver. However, increased risks of invasive treatment requirements for inappropriately compressed arterial/mixed ulcers due to false-negative results, and increased healing times due to delayed compression of false-positive test results mean that in most scenarios manual Doppler was less costly and had slightly higher quality-adjusted life-years than automated devices. Results are highly uncertain, dependent on many assumptions and should be interpreted cautiously.

Limitations and conclusions
The limited evidence identified for each automated device, especially in people with leg ulcers, and its clinical heterogeneity precludes any firm conclusions on the diagnostic performance and cost-effectiveness of these devices in clinical practice.