Phase 2 Study for Infrared Thermometry Used by Diabetic Patients at Home

SIGNIFICANCE & RATIONALE FOR PROPOSED PROJECT Foot problems are the most common complication in diabetics leading to hospitalization.1-5 Approximately one quarter of all hospital days for persons with diabetes are related to foot complications.4,5,8 In the United States there are approximately 120,000 non-traumatic lower extremity amputations performed each year.6,7 In the U.S., 45%-83% of all lower extremity amputations involve diabetics.1,9,5 Overall, patients with diabetes are 15-46 times more likely to have an amputation than patients without diabetes.11,14,15 It has been estimated that 5% to 15% of diabetics will have a lower extremity amputation in their lifetime.11 After their initial amputation 9-17% of diabetic patients will experience a second amputation within the same year12-17 and 25% to 68% of diabetics will have an amputation of the contralateral extremity within five years.18-20 The five-year survival rate after a lower extremity amputation ranges from 41% to 70%.19-21 Indeed, 10% of these patients die before leaving the hospital after a lower extremity amputation.7,9,20 National Initiatives: There are a number of initiatives by federal and state government organizations to prioritize efforts to reduce the burden of diabetes related amputations. Healthy People 2000 and Healthy People 2010 have set a goal of reducing the incidence of diabetes related amputation by 40%, and the U.S. Department of Health and Human Services has prioritized amputation reduction in minorities as one of its strategic Initiatives to Eliminate Racial and Ethnic Disparities in Health. Likewise, the Veterans Administration and Indian Health Service have prioritized amputation prevention for patients with diabetes. For instance, the VA has mandated the development of special programs to evaluate patients with diabetes, identify patients that fit a high-risk profile, and provide specialized treatment programs in order to decrease the impact of diabetes related complications within the Veterans Health Administration. Lower extremity complications in diabetics are common, costly and associated with a high rate of recurrence, morbidity and mortality. Several studies in the U.S. and Europe suggest that amputations and ulcerations can be prevented when special foot care and education are implemented. Despite these types of initiatives, increasing research knowledge, better re-vascularization and diagnostic procedures and an expanding armamentarium of new drugs and technology, the incidence of amputation has increased over the past few decades.15 Precursors to amputation: In diabetes, as in other chronic diseases, patient involvement to identify early warning signs of the disease process is imperative to reduce the incidence of complications and prevent morbidity. Many lower extremity complications involve sensory neuropathy as a pivotal component of the critical pathway for both the development of ulcers and amputations. Therefore, pain and loss of function, primary natural warning systems that alert us to take action and seek medical care, are faulty. Diabetic patients can hence sustain injuries that are not recognized until they are so severe that full thickness ulcerations result. The aim of this study was to further evaluate a tool to help high-risk diabetics identify areas on their feet that are inflamed and prone to ulceration before a wound develops at sites that would otherwise not be recognized as "symptomatic." Results of the Phase I study indicated that high-risk patients with diabetes can effectively use an infrared temperature device to monitor foot temperatures. Patients who used the device had significantly fewer foot complications compared to patients who received education, therapeutic shoes plus insoles and regular foot evaluations alone.

Foot ulcers are one of the most common precursors to diabetes related amputations.8,25 Other factors that have been associated with amputation, such as infection, faulty wound healing, and ischemia, usually do not cause tissue loss or amputation in the absence of a wound. Therefore, ulcer prevention is one of the foci of any amputation prevention program. Three primary pathways or mechanisms of injury have recently been identified in the development of foot ulcers They include wounds that result from ill-fitting shoes (low-pressure injuries that are associated with prolonged or constant pressure from narrow or short shoes), repetitive moderate forces on the sole of the foot, and from puncture wounds (high-pressure injuries with a single exposure of direct pressure). The most common mechanism involves the second scenario (receptive moderate force). Except for puncture wounds, areas that are likely to ulcerate have been associated with increased local skin temperatures due to inflammation and enzymatic autolysis of tissue. Several reports have suggested that wounds develop due to a cumulative effect of unrecognized repetitive injury over the course of several days. Identifying areas of injury by the presence of inflammation would then allow patients or health care providers to take action to decrease the inflammation before a wound develops.

Effectiveness of prevention: Several studies have suggested that foot complications can be prevented by a focused team approach to identify and treat lower extremity complications. This approach generally involves de-weighting pressure areas with special shoes, patient education and self-care practices, re-vascularization, optimal glucose control, infection control, use of appropriate referral patterns, and regular foot care.18, 26-30 Several studies have demonstrated a significant decrease in the incidence of ulceration and re-ulceration when therapeutic footwear, education, and regular diabetic foot care was provided. However, 19-28% of these patients still re-ulcerated within 12-18 months.26,31,32 Edmonds and coworkers18 reported a 26% re-ulceration rate in high-risk diabetics with special shoes and insoles compared to an 83% re-ulceration rate in patients that wore their own shoes. Likewise Uccioli26 reported a 28% re-ulceration rate in diabetics treated with custom shoes and insoles compared to 50% re-ulceration among patients without special footwear. In a descriptive report, Helm and co-workers32 reported a 19% re-ulceration over an 18-month period among patients that healed neuropathic ulcers in total contact casts. As in other studies, after wound closure patients received custom shoes or healing sandals and regular clinical follow-up care. All of these studies were performed at specialty foot centers with a focus on diabetes. Even in these centers, the risk of re-injury was very high.

Predicting impending injury: Our rationale for evaluating skin temperatures involves the search for a quantifiable, reproducible measurement of inflammation that can be used to identify pathologic processes before they result in ulcers. Inflammation is one of the earliest signs of foot ulceration. Five cardinal signs characterize inflammation: redness, pain, swelling, loss of function and heat. Many of these signs are difficult to assess objectively. In the neuropathic extremity, pain and disturbance of function may be absent because of neuropathy and thus are poor indicators of inflammation. In addition, swelling and redness are difficult to objectively grade from clinician to clinician or from visit to visit. Most lay people will not be able to understand or accurately evaluate these subtle parameters. However, temperature measurements can be easily performed by patients or their spouses and provide quantitative information that has been shown to be predictive of impending ulceration in diabetics with sensory neuropathy.

Since ulcers develop as a result of cumulative injury over the course of several days, patients need a mechanism to identify early warning signs of ulceration to prompt them to take appropriate action.44 The high re-ulceration rates reported in previous studies indicate that early warning signs are missed. A home temperature monitoring system for wound prevention is a similar concept to home glucose monitoring to help patients adjust their insulin. In both cases patients need frequent information about a health parameter that has the potential to change in a very short period of time. In both cases patients are taught to use the objective data provided from their home monitoring device to alter their behavior whether it is used to change insulin dosage or activity level. One of the barriers to lowering the incidence of ulcers and amputation is an objective mechanism that patients can use at home, such as a home monitoring system.