Volume Measures Using a Digital Image Analysis System are Reliable in Diabetic Foot Ulcers
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This process will differ between raters and within the same rater, and may be influenced by lighting, glare, and image focus. Another factor that can lead to unreliable volume measures is variation in patient and/or wound position that can occur between measurements by the same rater or between measurements of various raters. Patient/wound position may alter the wound margin shape and wound bed depth, both of which are critical to the VeVMD technique. All of these factors reduce the reliability of volume measures. Therefore, reliability needs to be examined to evaluate the dependability of VeVMD in determining wound volume.
The purpose of this study was to examine the reliability of wound volume measures obtained using VeVMD in a sample of plantar-surface diabetic foot ulcers (DFU). Plantar surface DFU are typically circular or elliptical and rarely present with irregular borders. Nevertheless, the careful monitoring of wound healing progress, achieved by reliable wound measures, is imperative in order to prevent complications, such as amputation. The specific aims of this study were to:
1. Identify the inter-rater reliability of DFU volume measurement using VeVMD.
Identify the intra-rater reliability of DFU volume measurement using VeVMD.
The current study was completed as part of a larger prospective study to examine bioburden predictors of DFU outcomes (NINR R01 NR009448 PI. Sue Gardner). A cross-sectional research design was used.
Setting and sample. Subjects in the primary study were recruited from a large academic medical center and a Department of Veterans’ Affairs Medical Center, both in the US Midwest. Adults with diabetes who were not taking long-term antibiotics and had a stable, nonvascular neuropathic ulcer on the plantar surface of the foot were recruited for participation in the study. Subjects with evidence of osteomyelitis were excluded. Subjects with full-thickness DFU (ie, extends through the dermal layer) were included in the primary study. Subjects from the primary study with superficial ulcers were excluded, due to the miniscule volume of these ulcers. Approval of the study was obtained from the institutional review board at both institutions. All subjects provided written, informed consent prior to study participation.
Wound volume measures. The primary study variable was wound volume, measured using the VeVMD software system. This software was downloaded on a Dell Latitude D630 laptop computer (Dell, Round Rock, TX). Digital images of study ulcers were obtained using a Canon PowerShot SX100 camera (Canon USA, Lake Success, NY) at 0.3 megapixel resolution using the “macro” function to enhance image clarity. The camera lens was zoomed in so that the ulcer field occupied the entire viewfinder window. The flash and focus features were set to “automatic.” Digital images contained the ulcer, a 3 cm2 orientation card, the subject ID number, and a single-point wound-depth indicator (ie, a marked cotton-tipped applicator placed at the deepest point of the wound base). At least 6 images were obtained and uploaded to the study computer and into the VeVMD software program. The software oriented each image to scale and to the plane of the ulcer using the 3 cm2 orientation card. The image with the highest degree of orientation accuracy was selected for all subsequent wound measurements.
Using this image, the ulcer outline was traced using the VeVMD “Shrink-Fit Tool.” This tool utilized a series of tracer points, connected by line segments, to outline the edge of the ulcer margin.