Assessment of signs of foot infection in diabetes patients using photographic foot imaging and infrared thermography.

BACKGROUND: Patients with diabetic foot disease require frequent screening to prevent complications and may be helped through telemedical home monitoring. Within this context, the goal was to determine the validity and reliability of assessing diabetic foot infection using photographic foot imaging and infrared thermography. SUBJECTS AND METHODS: For 38 patients with diabetes who presented with a foot infection or were admitted to the hospital with a foot-related complication, photographs of the plantar foot surface using a photographic imaging device and temperature data from six plantar regions using an infrared thermometer were obtained. A temperature difference between feet of >2.2 °C defined a "hotspot." Two independent observers assessed each foot for presence of foot infection, both live (using the Perfusion-Extent-Depth-Infection-Sensation classification) and from photographs 2 and 4 weeks later (for presence of erythema and ulcers). Agreement in diagnosis between live assessment and (the combination of ) photographic assessment and temperature recordings was calculated.
RESULTS: Diagnosis of infection from photographs was specific (>85%) but not very sensitive (<60%). Diagnosis based on hotspots present was sensitive (>90%) but not very specific (<25%). Diagnosis based on the combination of photographic and temperature assessments was both sensitive (>60%) and specific (>79%). Intra-observer agreement between photographic assessments was good (Cohen's κ=0.77 and 0.52 for both observers).
CONCLUSIONS: Diagnosis of foot infection in patients with diabetes seems valid and reliable using photographic imaging in combination with infrared thermography. This supports the intended use of these modalities for the home monitoring of high-risk patients with diabetes to facilitate early diagnosis of signs of foot infection.