Evaluating the effect of growing patient numbers and changing data elements in the National Surgical Quality Improvement Program (NSQIP) database over the years: a study of posterior lumbar fusion outcomes.

BACKGROUND CONTEXT: The use of national databases in spinal surgery outcomes research is increasing. A number of variables collected by the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) changed between 2010 and 2011, coinciding with a rapid increase in the number of patients included per year. However, there has been limited study evaluating the effect that these changes may have on the results of outcomes studies.

PURPOSE: The present study aimed to investigate the influence of changing data elements and growth of the NSQIP database on results of lumbar fusion outcomes studies.

STUDY DESIGN/SETTING: This is a retrospective cohort study of prospectively collected data.

PATIENT SAMPLE: The NSQIP database was retrospectively queried to identify 19,755 patients who underwent elective posterior lumbar fusion surgery with or without interbody fusion between 2005 and 2014. Patients were split into two groups based on year of surgery: 2,802 from 2005 to 2010 and 16,953 from 2011 to 2014.

OUTCOME MEASURES: The occurrence of adverse events after discharge from the hospital, within postoperative day 30, was determined.

METHODS: Preoperative characteristics and 30-day perioperative outcomes were compared between the era groups using bivariate analysis. To illustrate the effect of such changing data elements, the association between age and postoperative outcomes in the era groups was analyzed using multivariate Poisson regression. The present study had no funding sources, and there were no study-related conflicts of interest for any authors.

RESULTS: There were significant differences between the era groups for a variety of preoperative characteristics. Postoperative events such blood transfusion and deep vein thrombosis were also significantly different between the era groups. For the 2005-2010 cohort, age was significantly associated with septic shock by multivariate analysis. For the 2011-2014 cohort, age was significantly associated with septic shock, urinary tract infection, blood transfusion, myocardial infarction, and extended length of stay.

CONCLUSIONS: The NSQIP database has undergone substantial changes between 2005 and 2014. These changes may contribute to different results in analyses, such as the association between age and postoperative outcomes, when using older versus newer data. Conclusions from early studies using this database may warrant reconsideration.