Is a Left-to-Right >2.2°C Difference a Valid Measurement to Predict Diabetic Foot Ulceration in People with Diabetes and a History of Diabetic Foot Ulceration?

Monitoring foot skin temperatures at home have been shown to be effective at preventing the occurrence of diabetic foot ulcers. In this study, the construct validity of using >2.2 degrees C difference between contralateral areas on the foot as a warning sign of imminent ulceration is explored. Thirty participants with diabetes at high risk of ulceration (loss of protective sensation and previous ulceration and/or amputation) monitored their foot temperatures at six sites, four times a day for six days using a handheld infrared thermometer. Walking activity, time of day, and environmental temperature were also monitored and correlated with foot temperatures. We found that contralateral mean skin temperature difference was 0.78 degrees C at baseline. At single sites, left-to-right temperature differences exceeding the threshold were found in 9.6% of measurements (n = 365), which reduced to 0.4% when individually corrected and confirmed the next day. No correlation was found between contralateral temperature differences and activity, time of day, and environmental temperature. We conclude that using a >2.2 degrees C difference is invalid as a single measurement in people at high risk of ulceration, but the construct validity is appropriate if both individual corrections and next day confirmation are applied.