outcomes from the ACS-RC with a SAR score of 1 (no adjustment necessary) and 2 (risk somewhat higher than estimate) were compared with the rate of observed outcomes. Predictive accuracy at the individual level was completed using receiver operating characteristic area under the curve (AUC). Logistic regression with respect to mortality was performed over variables not considered by the ACS-RC. Further analysis was performed over a subgroup of patients with identified risk factors for mortality.Results: At the population level, ACS-RC underpredicted serious complications, surgical site infections, venous thromboembolisms, and unplanned return to the operating room, while overpredicting morality and cardiac complications (Table I). At the individual level, SAR1 was more predictive for serious complications (AUC ¼ 0.624), surgical site infections (AUC ¼ 0.610), and unplanned return to the operating room (AUC ¼ 0.541). Conversely, SAR2 was more predictive for mortality (AUC ¼ 0.709), cardiac complications (AUC ¼ 0.561), and venous thromboembolisms (AUC ¼ 0.539). Logistic regression identified history of cerebrovascular accident with a residual deficit (odds ratio [OR], 4.61; P ¼ .033) and ischemic rest pain as the indication for amputation (OR, 4.497; P ¼ .047) as independent risk factors for postoperative mortality (Table II). Analysis over a subgroup of patients with the specified risk factors (n ¼ 63) demonstrated relatively improved predictability at the population level with an observed morality rate (14.29%) between SAR1 (10.79%) and SAR2 (18.11%). However, at the individual level, the receiver operating characteristic revealed poor AUCs of 0.562 and 0.556 for SAR1 and SAR2, respectively.Conclusions: ACS-RC demonstrated moderate accuracy at the population level for outcomes of major lower extremity amputation; however, ACS-RC had less predictive accuracy at the individual level. History of cerebrovascular accident with residual deficit and ischemic rest pain as the indication for amputation were found to be predictors of postoperative mortality. In an isolated cohort with the aforementioned risk factors, the ACS-RC did not demonstrate increased predictability with the SAR; therefore, we cannot recommend utilizing this parameter based on these risk factors.
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