An explorative study on the validity of various definitions of a 2·2°C temperature threshold as warning signal for impending diabetic foot ulceration

Abstract

Home monitoring of skin temperature is effective to prevent diabetic foot ulceration. We explored the validity of various definitions for the >2·2°C left-to-right threshold used as a warning signal for impending ulceration. Twenty patients with diabetes and peripheral neuropathy monitored their skin temperature with an infrared thermometer at the plantar hallux, metatarsal heads, midfoot and heel four times a day for 6 consecutive days. Environmental temperature and walking activity were monitored and associated with foot temperature. The average temperature difference between feet was 0·65°C. At single locations, a left-to-right temperature difference of >2·2°C was found 245 times (8·5% of measurements). Confirmation of these above-threshold readings on the following day was found seven times (0·3%). Corrected for individual left-to-right mean foot temperature differences, this reduced to four (0·2%). No ulcers developed in the week after monitoring. Left-to-right foot temperature differences were not significantly correlated with walking activity, environmental temperature or time of day. The >2·2°C left-to-right foot temperature threshold for impending ulceration is not valid as single measurement, but validity improves to acceptable levels when an above-threshold temperature difference is confirmed the following day and further improves with individual correction. The threshold is independent of time of day, environmental temperature and walking activity.