Deriving ICD-9 and ICD-10 Codes For Identifying and Following Patients with Diabetic Lower Extremity Ulcers
- •Type of Research: Methodologic study for identifying clinical cohorts using Medicare claims data.
- •Key Findings: We identified 45 ICD-9 and 304 ICD-10 codes for identifying patients with lower extremity ulceration using the methods described within. We further demonstrated how these codes offer a mechanism for stratifying groups of patients into differential risks of amputation.
- •Take home Message: Using the methods described, we offer investigators a universally applicable approach to identify patients with lower extremity ulceration in large data sets. We also demonstrate how this might be used in risk stratifying patients at risk for amputation.
Administrative claims data offer a rich data source for clinical research. However, its application to the study of diabetic lower extremity ulceration is lacking. Our objective was to create a widely applicable framework by which investigators might derive and refine ICD-9 and ICD-10 codes for use in identifying diabetic, lower extremity ulceration.
Methods and Results
We created a 7-step process to derive and refine ICD-9 and ICD-10 coding lists for use in identifying diabetic lower extremity ulcers. This process begins with defining the research question and initial identification of a list of ICD-9 and ICD-10 codes for defining the exposures or outcomes of interest. Codes are then applied to claims data, and rates of clinical events examined for consistency with prior research and changes across the ICD-9 to ICD-10 transition. ICD-9 and ICD-10 codes are then cross referenced with each other, and the lists further refined. Using this method, we started with 8 ICD-9 and 43 ICD-10 codes used to identify lower extremity ulcers in patients with known diabetes and peripheral arterial disease and examined the association of ulceration with lower extremity amputation. After refinement we were left with 45 ICD-9 codes and 304 ICD-10 codes. We then grouped the codes into 8 clinical exposure groups and examined rates of amputation as a rudimentary test of validity. We found that the rate of lower extremity amputation correlated with severity of lower extremity ulceration.
We identified 45 ICD-9 and 304 ICD-10 ulcer codes which identified patients at risk for amputation from diabetes and peripheral artery disease. While further chart-level validation remains to be accomplished, these codes can be used for claims-based risk-stratification for long-term outcome assessment in the treatment of patients at risk for limb loss.