The Validity and Reliability of Diagnosing Foot Ulcers and Pre-Ulcerative Lesions in Diabetes Using Advanced Digital Photography

Background: The goal of this study was to determine the validity and reliability of assessing the presence of plantar foot ulceration and pre-ulcerative lesions in diabetes patients from digital photographs that were produced using a new photographic foot imaging device. Methods: In 32 diabetes patients who had a foot ulcer or were at high risk of ulceration (a total of 60 feet), high-quality photographic images of the plantar foot surface were collected. Each foot was assessed live, from photographs 2 weeks later, and again 4 weeks later for the presence of an ulcer, abundant callus, or the absence of signs. Each foot was assessed by four independently operating foot care specialists. Agreement scores were calculated using kappa values (range, 0-1). Sensitivity and specificity scores were also calculated. Results: Foot ulceration was cumulatively scored 59 times, callus 78 times, and absence of signs 149 times during live assessment. Agreement with photographic assessment was very good for ulcer (kappa = 0.87) and absence of signs (kappa = 0.83) and good for callus (kappa = 0.61). Sensitivity and specificity were high for ulcer (88% and 98%, respectively), callus (69% and 89%, respectively), and absence of signs (both 90%). Intra-observer agreement between repeated photographic assessments was good to excellent for all outcomes and observers (kappa between 0.70 and 1.00). Inter-observer agreement for photographic assessments was good for ulcer (kappa = 0.72-0.88) and absence of signs (kappa = 0.59-0.75) and moderate to good for callus (kappa = 0.48-0.73). For live assessment, inter-observer agreement scores were only slightly higher. Conclusions: The data illustrate that diabetic foot ulcers and pre-ulcerative lesions can be diagnosed in a valid and reliable manner by trained professionals from digital photographs produced with the foot imaging device. This supports the intended use of the device as a telemedical monitoring tool in the home environment for early detection of diabetic foot disease and prevention of severe complications in high-risk diabetes patients.