A New Mobile Application for Standardizing Diabetic Foot Images

Abstract

Background: We describe the development of a new mobile app called "FootSnap," to standardize photographs of diabetic feet and test its reliability on different occasions and between different operators.

Methods: FootSnap was developed by a multidisciplinary team for use with the iPad. The plantar surface of 30 diabetic feet and 30 nondiabetic control feet were imaged using FootSnap on two separate occasions by two different operators. Reproducibility of foot images was determined using the Jaccard similarity index (JSI).

Results: High intra- and interoperator reliability was demonstrated with JSI values of 0.89-0.91 for diabetic feet and 0.93-0.94 for control feet.

Conclusions: Similarly high reliability between groups indicates FootSnap is appropriate for longitudinal follow-ups in diabetic feet, with potential for monitoring pathology.

Keywords: app; diabetic foot; image; lesion; ulcer.

Conflict of interest statement

Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.

Flow chart of FootSnap. The app will first check if this is a new experiment (as shown in the diamond shape of the flow chart). If this is a new experiment, the app will create a new experiment, capture the foot image, generate a ghost image, and save the images to the internal storage. Otherwise the app will retrieve the existing experiment and load the ghost image. The user will align the foot to the ghost image, capture the foot image, and save the image to the internal storage.

Figure 2.

(A) Illustration of the experimental setup for using FootSnap. (B) An image being captured by the operator using the ghost image facility (white outline around the foot) within FootSnap.

Figure 3.

Inter- and intraoperator reliability for FootSnap in capturing (A) diabetic feet and (B) control feet. Data are mean and SD (N = 60 feet). A Jaccard similarity index value of 1 indicates perfect agreement between the two images in terms of shape description. Intra 1 and Intra 2 are the two different operators.

Figure 4.

Intraoperator reliability for FootSnap for two separate operators capturing (A) diabetic feet and (B) control feet. Values shown are for individual feet (N = 60 across A and B). A Jaccard similarity index value of 1 indicates perfect agreement between the two images in terms of shape description.

Figure 5.

Interoperator reliability (between operators 1 and 2) for FootSnap capturing (A) diabetic feet and (B) control feet. Values shown are for individual feet (N = 60 across A and B). A Jaccard similarity index value of 1 indicates perfect agreement between the two images in terms of shape description.