1493. Assessing the Performance of NSQIP Surgical Risk Calculator in Elective Spine Surgery: Insights from Patients Undergoing Single-level Posterior Lumbar Fusion

Authors: Mohamad Bydon, MD, FAANS ; Arjun Sebastian, MD; Anshit Goyal, MBBS; Mohammed Alvi, MBBS; Waseem Wahood, MS; Yagiz Yolcu, MD; Mohamed Elminawy; Elizabeth Habermann (Rochester, MN)

Introduction: The American College of Surgeons-National Surgical Quality Improvement Program (ACS-NSQIP) Surgical Risk Calculator (SRC) was a tool developed to use 21 individual patient characteristics to make predictions for occurrence of 13 general and 2 procedure specific outcomes. Literature on the role of NSQIP-SRC in spine surgery is sparse. The goal of this study was to evaluate the performance of the SRC in predicting outcomes in patients receiving posterior lumbar fusion. Methods: The ACS-NSQIP user file for 2015 was queried for patients with age≥18 undergoing single level posterior lumbar fusion (PLF) surgery. Individual patient characteristics were entered into the online risk calculator interface to retrieve the predicted estimated risk for perioperative outcomes and complications including surgical site infection, readmissions, reoperations, major complication, any complication and mortality. Following this, predictive performance was analyzed by computing brier score, c-statistic and sensitivity values for all observed outcomes. Results: A total of 2808 undergoing single-level PLF patients were included in the analysis with 53.7% (1510) females. Overall, a very low incidence of 30-day postoperative complications was observed with the procedure (0.9%-6.3%). Poor predictive performance was found for all outcomes including readmissions (c-statistic=0.63, sensitivity=15.28%, brier score=0.048) and returns to OR (c-statistic=0.63, sensitivity=15.28%, brier score=0.048). The best performance was observed for venous thromboembolism (c-statistic=0.66, brier score=0.008) although sensitivity was poor (3.85%) on account of low incidence. Predictive performance for length of stay revealed good agreement between observed and predicted values with the exception of prolonged predicted hospital stays (>3.5 days). Conclusion: This study assessed the performance of the risk calculator for a homogenous population of patients undergoing a single level posterior lumbar fusion. Although the calculator did not fare well in predicting most outcomes, results need to be interpreted in the context of the low incidence rate of such outcomes.