System for Prediction of Recurrent DFU
D
iabetic foot ulcers (DFU) are a common,
limb-threatening, and expensive complication
of diabetes (1,2) . Of the ;30 million patients with
diabetes in the U.S., 1.7million suffer one or more
DFU annually (3) . Conservative estimates of DFU-
related direct costs in the U.S. exceed $17 billion (2,4) .
Those who have recently healed from a DFU episode
are especially likely to suffer reulceration (1,5–9) . A
principal goal of care for these patients is to maintain
the integrity of the newly formed epithelium and
allow the underlying tissue to complete remodeling.
Unfortunately, caring for the patient in remission
following a DFU episode has proven challenging
under standard practice. Numerous prospective
studies have explored how ulcer-free survival is
impacted not only by underlying comorbidities, but
also by the duration since the patient most recently
healed from a DFU episode (1,5–9) . These investigations
suggest that between 30 and 40% of patients
experience a recurrent DFU in the year after healing.
Contrast this with the baseline incidence among all
patients with diabetes, which has been measured
between 3.6 and 5.8% (10,11) . Thus, a better approach
focused on predicting DFU to enable targeted
preventative therapies during this critical period may
significantly improve patient outcomes and reduce
DFU-related costs (12) .
Asymmetry analysis coupled with early offloading
of foot pressure has been shown to reduce DFU
incidence by; 70% across three randomized controlled
trials (15–17) . An independent systematic review and
meta-analysis determined the summary odds ratio
(OR) of the three trials to be 3.84 (95% CI 1.50–6.17)
(18)
. The threshold most commonly used for starting
preventative therapy has been 2.22°C (4°F) over at
least 2 consecutive days, although no studies have
been published to derive or optimize this threshold.
Despite evidence from multiple randomized
controlled trials and inclusion in three clinical
practice guidelines (19–21) , temperature monitoring
remains uncommon in practice. This may be because
of challenges with previous temperature-monitoring
technologies, including onerous patient workflow and
poor usability.
A telemedicine foot mat has been developed to
encourage adoption of daily foot temperature
monitoring in accordance with existing practice
guidelines. We therefore undertook this investigation
with the following objectives: 1) evaluate the
effectiveness of the foot mat as an early predictor
of recurrent plantar DFU in high-risk patients, 2)
determine participant adherence to daily use of the
mat over time, and 3) understand user perceptions of
the mat and ease of use.
Skin-temperature monitoring first emerged in the
1970s as a potentially useful tool for identifying
patients at risk for ulceration (13,14) . For those wounds
that are not because of acute injury, the hypothesized
mechanism is believed to be repetitive microtrauma
leading to localized enzymatic autolysis of tissue and
inflammation. The temperature-monitoring approach
best supported in the literature (15–18) uses plantar foot
temperature asymmetry between a pair of feet to
identify patients with elevated risk. This practice is
referred to in this study as “asymmetry analysis.”
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RESEARCH DESIGN AND METHODS
W
e conducted a prospective, multicenter,
cohort study to evaluate a novel remote
foot-temperature monitoring system (ClinicalTrials.
gov Identifier NCT02647346). The study device is
a wireless thermometric foot mat. We enrolled 132
diabetic participants, each with history of healed
DFU prior to enrollment, across seven outpatient sites
in the U.S. representing varied care environments.