Changes in classifications of chronic lower-limb wound codes in patients with diabetes: ICD-9-CM versus ICD-10-CM

Objective: To determine the sensitivity and specificity of International Classification of Diseases, Ninth Edition, Clinical Modification (ICD-9-CM) and ICD-10-CM codes for individuals with diabetes and foot ulcers. Design and Methods: Wound care providers and researchers are concerned about the potential impacts when the United States transitions from ICD-9-CM to ICD-10-CM. To identify the impact on diabetic foot ulcers, health history and wound variables were prospectively assessed with criterion-standard data from a prospective study of 49 patients with 65 foot ulcer episodes representing 81 incident foot ulcers. The ICD-9-CM and ICD-10-CM code sets were mapped to correctly classify individuals with diabetes and foot ulcers. Results: Frequencies for health history variables were similar in both systems. The ICD-9 code did not capture any data on laterality (left or right) or ulcer depth/severity. The ICD-9 captured 69 of 81 incident ulcers (85%) and 94% of heel and midfoot ulcers, whereas the ICD-10 code captured 78 of 81 incident ulcers (96%) and all incident heel or midfoot ulcers. Sensitivity and specificity for ulcer characteristics were consistently lower in ICD-9 than in ICD-10. Conclusions: The ICD-9 and ICD-10 are similar for data capture on health history variables, but wound variables are captured more accurately using ICD-10. The increased specificity of ICD-10 for ulcer location and severity improves identification and tracking ulcers during an episode of care.