Correlation of perioperative risk scores with hospital costs in neurosurgical patients

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The American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) online surgical risk calculator uses inherent patient characteristics to provide predictive risk scores for adverse postoperative events. The purpose of this study was to determine if predicted perioperative risk scores correlate with actual hospital costs.


A single-center retrospective review of 1005 neurosurgical patients treated between September 1, 2011, and December 31, 2014, was performed. Individual patient characteristics were entered into the NSQIP calculator. Predicted risk scores were compared with actual in-hospital costs obtained from a billing database. Correlational statistics were used to determine if patients with higher risk scores were associated with increased in-hospital costs.


The Pearson correlation coefficient (R) was used to assess the correlation between 11 types of predicted complication risk scores and 5 types of encounter costs from 1005 health encounters involving neurosurgical procedures. Risk scores in categories such as any complication, serious complication, pneumonia, cardiac complication, surgical site infection, urinary tract infection, venous thromboembolism, renal failure, return to operating room, death, and discharge to nursing home or rehabilitation facility were obtained. Patients with higher predicted risk scores in all measures except surgical site infection were found to have a statistically significant association with increased actual in-hospital costs (p < 0.0005).


Previous work has demonstrated that the ACS NSQIP surgical risk calculator can accurately predict mortality after neurosurgery but is poorly predictive of other potential adverse events and clinical outcomes. However, this study demonstrates that predicted high-risk patients identified by the ACS NSQIP surgical risk calculator have a statistically significant moderate correlation to increased actual in-hospital costs. The NSQIP calculator may not accurately predict the occurrence of surgical complications (as demonstrated previously), but future iterations of the ACS universal risk calculator may be effective in predicting actual in-hospital costs, which could be advantageous in the current value-based healthcare environment.

ABBREVIATIONS ACS NSQIP = American College of Surgeons National Surgical Quality Improvement Program; LOS = length of hospital stay; OR = operating room; SSI = surgical site infection; UTI = urinary tract infection; VTE = venous thromboembolism.

Article Information

Correspondence Sasha Vaziri: University of Florida, Gainesville, FL.

INCLUDE WHEN CITING Published online February 15, 2019; DOI: 10.3171/2018.10.JNS182041.

S.V. and J.M.A. contributed equally to this work.

Disclosures Dr. Hoh receives a stipend of $7500 per year for serving on the editorial board of The Spine Journal.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Pearson correlation coefficients (unadjusted) between each neurosurgical encounter cost category and all predicted postoperative risk scores. All correlation coefficients are statistically significant except for encounters highlighted in gray and noted with NS. NS = not significant. Figure is available in color online only.

  • View in gallery

    Pearson correlation coefficients (unadjusted) between perioperative complications and all predicted postoperative risk scores. All correlation coefficients are statistically significant except for cardiac complications and renal failure (dark gray), which did not have the minimum number of events to complete the analysis and cost encounters highlighted in light gray and noted with NS. NA = not analyzed. Figure is available in color online only.



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