Original Research

Remote Temperature Monitoring of the Diabetic Foot: From Research to Practice

Fed Pract. 2020 March;37(3):114-124

References

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Remote Temperature Monitoring

The objective of daily foot temperature monitoring is to identify impending inflammatory foot conditions, such as DFUs, infection, and acute Charcot neuroarthropathy episodes. The patient and care team then act to resolve the cause of detected inflammation before clinical presentation (prevention) and begin treatment earlier than would otherwise be possible to avoid expensive complications, such as infection (early detection). Preventive therapies are low risk to the patient and inexpensive.

RTM is recommended by multiple clinical practice guidelines, including those of the International Working Group on the Diabetic Foot, the American College of Foot and Ankle Surgeons, and the Wound Healing Society.^24-26 Its use is supported by evidence from 3 National Institutes of Health-funded and well-designed randomized controlled trials, 1 of which was additionally supported by a VA Health Services Research and Development Service Merit Award.^21-23^,28 Conducted between 2004 and 2007, these studies demonstrated the potential to reduce foot ulcer incidence by as much as 85% using a dermal thermometer to identify inflammation and prompt decreased ambulation. Investigators established a clinical monitoring protocol comparing the temperatures between 6 matched locations on the left and right feet. Persistent differences in contralateral temperatures exceeding 2.2°C (4.0°F) were used as a marker for elevated risk and to initiate preventive care. Based on the encouraging results from these studies, a 2017 effectiveness review prepared for the Agency for Healthcare Research and Quality concluded that “home monitoring of foot skin temperature is effective for reducing foot ulcer incidence and recurrence.”²⁹

Accuracy of RTM

A 2017 longitudinal study (NCT02647346) has provided novel data to advance understanding of RTM for the prediction and prevention of DFUs.³⁰ This study was the first to systematically analyze the accuracy of RTM over different monitoring thresholds. The results enable practitioners to deliver risk-stratified preventive care. Policy makers can use the data from this study to weigh the cost and benefits of RTM for population health.

The multicenter trials had 129 participants from 4 VA health care systems: VA Long Beach Healthcare System in California, Miami VA Healthcare System in Florida, Phoenix VA Healthcare System in Arizona, and VA West Los Angeles Healthcare System in California. Each participant was followed for 34 weeks under standard preventive foot care and was instructed to step on a telemedicine SmartMat (Podimetrics, Inc) RTM mat for 20 seconds daily. Participants and investigators were blinded to the temperature data so that the accuracy of temperature monitoring could be assessed. All participants had a history of T2DM and healed DFU. Principal exclusion criteria included unhealed plantar wound, history of proximal lower extremity amputation (ie, above ankle), active Charcot foot disease, and comorbidities that could potentially inhibit an inflammatory response, such as end-stage renal disease, active malignancy, and immunosuppressive diseases.

The investigators reported that RTM with the study mat detected 97% of nonacute plantar DFUs using the most commonly studied threshold (sustained 2.2°C temperature difference). The lead time averaged 37 days before clinical identification of the wound under standard care. Although the false-positive rate of 57% was high, corresponding to approximately 3.0 notifications per patient per year on average in the research setting, it is important to note that this study only considered the prediction of plantar DFUs. Thus, detection of foot inflammation secondary to other conditions, such as preulcerative lesion, dorsal wound, Charcot neuroarthropathy, or foot infection, were reported as a false positive per the study’s definitions. Further, Crisologo and Lavery noted in a translational medicine summary of this research, because the intervention is noninvasive and minimally impactful to the patient and the health care system, “the potential to arrest re-ulceration is worth the perceived inconvenience to the patient.”³¹

Secondary outcomes related to adherence and ease of use were encouraging. Eighty-eight percent of participants reported that the mat was “very easy to use,” the highest possible score, and 98% were able to set up the mat for home use without difficulty. At the end of the 34-week study, more than 74% of participants remained engaged in routine use of the mat under a per-protocol assessment of adherence. These results are especially impressive given the documented poor adherence of at-risk patients to routine use of therapeutic footwear, which has been reported to be as low as 15%.³²