Summary

Foot skin temperature measurements allow type-2 diabetics to acquire early warning of the likelihood of ulceration, according to this study.

Introduction

Most diabetic patients have probably learned the necessity of taking care of their own health, to a great extent. They must watch what they eat, take their medications, test their blood glucose, and exercise regularly. Most importantly, they must remain alert for any signs of the major complications of the disease - atherosclerosis leading to coronary heart disease, peripheral artery disease, eye problems (retinopathy), kidney disease, neuropathy, and foot problems.

Lower limb complications of diabetes often involve peripheral neuropathy, a result of diabetes in which there is often loss of sensation in the feet. The risk here is that people don't recognize that their feet may be undergoing injury until a wound develops. By this time troublesome skin ulceration is not far away, which becomes infected and slow to heal. Healing is often severely delayed due to poor blood supply (peripheral arterial disease and venous stasis), and even amputation may become necessary as the condition progresses.

Inflammatory changes (warmth, redness, pain, and swelling) precede the more visible breakdown of the skin in diabetic ulceration. Texas and Arizonan physicians have therefore explored the possibility of diagnosing a pre-ulcer stage in high-risk diabetics. They evaluated the effectiveness of home skin temperature monitoring, and reported their findings in the American Journal of Medicine.

What was done

US Department of Veterans Affairs patients volunteered for this study. There were 225 type-2 diabetics at high risk of foot ulceration - they had neuropathy and deformity with limited joint mobility, or a previous history of ulceration. They were randomly assigned to either a standard therapy or a dermal thermometry group. Both groups received therapeutic footwear, diabetic foot education, and regular foot care; they performed a standardized foot inspection daily, and recorded their findings in a log.

The dermal thermometry group subjects used an infrared skin thermometer to measure the temperature at 6 sites on both feet twice a day. A difference of 40 or more (Fahrenheit) between corresponding sites on the left and right foot was reported at once, and activity was reduced until the temperatures had normalized.

Stand therapy group members were instructed to report immediately any foot abnormality they detected.

The study lasted 18 months, with data evaluation at 3 month intervals during this period. Ulceration was defined as full-thickness loss of skin or involvement of deeper structures (connective tissue, fat, muscle).

What was found

The average age of the subjects was 69; the vast majority (96%) was male. They had had diabetes for an average of 13 years, and their HbA1c averaged 7.75.

In the standard therapy group, 12.2% of the subjects developed ulcers over the 18-month period. In the thermometry group, only 4.7% developed ulcers. After adjusting for differences in age, minority status, and risk factors, it was found that regular full temperature measurements were linked to a significant longer time to development of ulceration.

In those patients who experienced ulceration in the temperature-measuring group, the average temperature difference to the other foot in the week before ulceration was 4.8 times higher than a random 7-day sample of 50 subjects who didn't develop an ulcer.

Conclusions

The results of this study are clear cut. In diabetics, raised foot skin temperatures - by more than 40 (Fahrenheit), about 4 times higher than 'normal' fluctuations - precede visual signs of threatened ulceration, and can be used to institute preventive measures, such as reduced activity. This is an important finding, as there are few effective therapies to help high-risk diabetics prevent the development of foot ulcers. Getting early warning of trouble allows patients to reduce the possible stimuli to ulceration - overactivity in unsuitable footwear, exposure to damp or cold environment, and so on.

The preventive technique requires a little work by the patient - twice daily temperature measurements at 6 skin sites on each foot - but this should prove worthwhile. Foot ulcers in diabetics are notoriously slow to heal, and cause their own level of disability. The thermometry regime should fit easily with other type-2 diabetic self-management activities, allowing patients to have a full and satisfying lifestyle.