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Original research
Assessing the volume–outcome relationship of carotid artery stenting in nationwide administrative data: a challenge of patient population bias
  1. Stefan W Koester,
  2. Tyler S Cole,
  3. Anna R Kimata,
  4. Kevin L Ma,
  5. Dimitri Benner,
  6. Joshua S Catapano,
  7. Kavelin Rumalla,
  8. Michael T Lawton,
  9. Andrew F Ducruet,
  10. Felipe C Albuquerque
  1. Department of Neurosurgery, Barrow Neurological Institute, Phoenix, Arizona, USA
  1. Correspondence to Dr Felipe C Albuquerque, Department of Neurosurgery, Barrow Neurological Institute,St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA; Felipe.Albuquerque{at}


Background Studies have shown an association between surgical treatment volume and improved quality metrics. This study evaluated nationwide results in carotid artery stenting (CAS) procedural readmission rates, costs, and length of stay based on hospital treatment volume.

Methods We used the Nationwide Readmissions Database for carotid stenosis from 2010 to 2015. Patients receiving CAS were matched based on demographics, illness severity, and relevant comorbidities. Patients were matched 1:1 between low- and high-volume centers using a non-parametric preprocessing matching program to adjust for parametric causal inferences. Nearest-neighbor propensity score matching was performed using logit distance.

Results Low- and high-volume centers admitted a mean (SD) of 4.68 (3.79) and 25.10 (16.86) patients undergoing CAS per hospital, respectively. Comorbidities were significantly different and initially could not be adequately matched. Because of significant differences in baseline patient population characteristics after attempted matching between low- and high-volume centers, we used propensity adjustment with multivariate analysis. Using this alternative approach, no significant differences were observed between low- and high-volume centers for the presence of any complication, postoperative stroke, postoperative myocardial infarction, and readmission at 30 days.

Conclusion In 1:1 nearest-neighbor matching with a high number of patients, our analysis did not result in well-matched cohorts for the effect of case volume on outcomes. Comparing analytical techniques for various outcomes highlights that outcome disparities may not be related to quality differences based on hospital size, but rather variability in patient populations between low- and high-volume institutions.

  • Statistics
  • Stenosis
  • Stent
  • Stroke

Data availability statement

Data are available upon reasonable request.

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Data availability statement

Data are available upon reasonable request.

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  • Contributors Conception and design: SWK, TSC, JSC, KR. Acquisition of data: SWK, TSC. Analysis and interpretation of data: SWK, TSC, ARK, KLM, DB. Drafting the article: SWK, ARK, KLM, DB. Critically revising the article: SWK, TSC, JSC, KR, ARK, KLM, DB, MTL, AFD, FCA. Review of final version of the manuscript and approval for submission: SWK, TSC, JSC, KR, ARK, KLM, MTL, AFD, FCA. Statistical analysis: SWK, TSC. Administrative/technical/material support: MTL, AFD, FCA. Study supervision: JSC, TSC, MTL, AFD, FCA. The guarantor of the study is FCA.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests AFD and FCA serve on the editorial board of the Journal of NeuroInterventional Surgery. AFD is a consultant for Medtronic, Penumbra, Stryker, Cerenovus, Koswire, and Oculus.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.