352 Validation of inpatient ICD9 diagnosis codes as predictors of venous leg ulcers

Abstract

Venous Leg Ulcers (VLU) comprise about 70% of lower leg wounds and cost more than 14 billion USD per year. There is a need to establish VLU epidemiologic trends in order to develop better diagnostic, preventive, and treatment strategies. Patients with VLU are often admitted to the hospital; however, epidemiological study of this important patient subset is challenged by lack of validated database search protocol. Initially, five International Classification of Diseases (ICD) 9 codes were identified for their relationship with VLUs. The codes were 454.0 (leg varicosity with ulcer), 454.2 (varicose leg ulcer/inflammation), 459.11 (postphlebitic syndrome with ulcer), 707.9 (chronic skin ulcer NOS), and 707.10 (ulcer of lower limb NOS). A list of inpatient admissions at the University of Miami Hospital where any of these five codes were entered was obtained. A total of 320 unique admissions were identified. A chart review of these patients was performed, focusing on the admission where the diagnosis code was inserted. The ICD9 code was considered to successfully predict a VLU if the wound was located in the gaiter area and had either relevant clinical findings, a positive venous study, and/or a diagnosis of VLU written in the physician note. Excluded were subjects with an ulcer with a clear wound etiology other than VLU. After analysis, 454.0 in addition to any other code was the most accurate predictor of VLU, with a sensitivity of 77% and a specificity of 79%. In this group, the positive and negative predictive values (PPV, NPV) were 37% and 96%, respectively. Also, patients with only the 454.0 code without any of the other above codes had the highest sensitivity 100% (8/8); however, the PPV was low at 8.6%. In conclusion, patients admitted with an ICD9 code of 454.0 have a high probability of VLU, however there is a high percentage of patients with this condition who will not receive this diagnosis code.