Do we really know our patient population in database research? A comparison of the femoral shaft fracture patient populations in three commonly used national databases.

Abstract

While use of large national clinical databases for orthopaedic trauma research has increased dramatically, there has been little study of the differences in populations contained therein. In this study we aimed to compare populations of patients with femoral shaft fractures across three commonly used national databases, specifically with regard to age and comorbidities. Patients were identified in the Nationwide Inpatient Sample (NIS), National Surgical Quality Improvement Program (NSQIP) and National Trauma Data Bank (NTDB). The distributions of age and Charleston comorbidity index (CCI) reflected a predominantly older population with more comorbidities in NSQIP (mean age 71.5; sd 15.6), mean CCI 4.9; sd 1.9) than in the NTDB (mean age 45.2; sd 21.4), mean CCI = 2.1; sd 2.0). Bimodal distributions in the NIS population showed a more mixed population (mean age 56.9; sd 24.9), mean CCI 3.2; sd 2.3). Differences in age and CCI were all statistically significant (p < 0.001). While these databases have been commonly used for orthopaedic trauma research, differences in the populations they represent are not always readily apparent. Care must be taken to understand fully these differences before performing or evaluating database research, as the outcomes they detail can only be analysed in context. Researchers and those evaluating research should be aware that orthopaedic trauma populations contained in commonly studied national databases may differ substantially based on sampling methods and inclusion criteria.