Efficacy of VBHOM to predict outcome following major lower limb amputation

Purpose: This study tests an existing Vascular Biochemistry and Haematology Outcome Model (VBHOM) on independent data and presents further refinements to the model. Methods: Data from 306 patients who underwent lower limb amputation over a 4-year period were collated. Urea, creatinine, sodium, potassium, hemoglobin, white cell count, albumin, age, gender, mode-of-admission, and short-term mortality events were extracted from the database. This study tests an existing model and trains a new model for predicting mortality using forward stepwise logistic regression. Results: The existing model suggests a significant lack of fit (c-index = 0.665, P =.04). For the exception of gender and mode-of-admission, all predictor variables had significant univariate associations with short-term mortality (P <.05). The refined model included age, sodium, potassium, creatinine, and albumin and had good discriminatory power (c-index = 0.8, no evidence of lack of fit, P =.616). Conclusions: Our simplified model had good predictive ability and suggests redundancy in input variables used by the existing models.