External Validation of Surgical Risk Preoperative Assessment System in Pulmonary Resection

Background: Accurate preoperative risk assessment is necessary for informed decision making for patients and surgeons. Several preoperative risk calculators are available but few have been examined in the general thoracic surgical patient population. The Surgical Risk Preoperative Assessment System (SURPAS), a risk-assessment tool applicable to a wide spectrum of surgical procedures, was developed to predict the risks of common adverse postoperative outcomes using a parsimonious set of preoperative input variables. We sought to externally validate the performance of SURPAS for postoperative complications in patients undergoing pulmonary resection. Methods: Between January 2016 and December 2018, 2514 patients underwent pulmonary resection at our center. Using data from our institution's prospectively maintained database, we calculated the predicted risks of 12 categories of postoperative outcomes using the latest version of SURPAS. Performance of SURPAS against observed patient outcomes was assessed by discrimination (concordance index) and calibration (calibration curves). Results: The discrimination ability of SURPAS was moderate across all outcomes (concordance indices, 0.640 to 0.788). Calibration curves indicated good calibration for all outcomes except infectious and cardiac complications, discharge to a location other than home, and mortality (all overestimated by SURPAS). Conclusions: SURPAS demonstrates outcomes for pulmonary resections with reasonable predictive ability. Discretion should be applied when assessing risk for postoperative infectious and cardiac complications, discharge to a location other than home, and mortality. Although the parsimonious nature of SURPAS is one of its strengths, its performance might be improved by including additional factors known to influence outcomes after pulmonary resection, such as sex and pulmonary function.