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Local Instrumental Variable Methods to Address Confounding and Heterogeneity when Using Electronic Health Records: An

Silvia Moler-Zapata1, Richard Grieve1, David Lugo-Palacios1

  • 1Department of Health Services Research and Policy, London School of Hygiene & Tropical Medicine, London, UK.

Medical Decision Making : an International Journal of the Society for Medical Decision Making
|May 24, 2022
PubMed
Summary
This summary is machine-generated.

Local instrumental variable (LIV) methods applied to electronic health records (EHRs) reveal cost-effectiveness of emergency surgery (ES) varies by patient frailty. This research highlights the importance of considering heterogeneity in treatment effects for common acute conditions.

Keywords:
cost-effectiveness analysisemergency surgeryheterogeneous treatment effectsinstrumental variablepersonalized medicine

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Area of Science:

  • Health Economics
  • Medical Informatics
  • Surgical Outcomes Research

Background:

  • Electronic health records (EHRs) are valuable for comparative effectiveness research but require methods to address confounding and heterogeneity.
  • Local instrumental variable (LIV) methods can mitigate these challenges but have not been widely applied to EHR data.
  • Evaluating the cost-effectiveness of emergency surgery (ES) using EHRs necessitates robust analytical approaches.

Purpose of the Study:

  • To critically examine the application of a Local instrumental variable (LIV) approach to EHR data for assessing the cost-effectiveness of emergency surgery (ES).
  • To evaluate ES cost-effectiveness for common acute conditions including appendicitis, diverticular disease, and abdominal wall hernia.
  • To address confounding and treatment effect heterogeneity in comparative effectiveness research using EHRs.

Main Methods:

  • Utilized hospital episodes statistics (HES) data for 268,144 appendicitis, 138,869 diverticular disease, and 106,432 hernia patients in England (2010-2019).
  • Employed a Local instrumental variable (LIV) approach, using hospital-specific ES rates as the instrument for ES receipt.
  • Compared LIV findings with traditional instrumental variable and risk-adjustment methods, assessing cost-effectiveness and heterogeneity.

Main Results:

  • The instrumental variable (hospital ES rate) was strong and minimized covariate imbalance.
  • For diverticular disease, LIV indicated ES was cost-effective, contrasting with traditional methods, though with wide uncertainty.
  • All three conditions showed heterogeneity in ES cost-effectiveness by subgroup; notably, ES was not cost-effective for patients with severe frailty.

Conclusions:

  • Local instrumental variable (LIV) methods can be effectively combined with electronic health records (EHRs) to assess the cost-effectiveness of routinely provided interventions.
  • This approach fully recognizes and quantifies heterogeneity in treatment effects across different patient populations.
  • Findings underscore the need for individualized cost-effectiveness evaluations to inform clinical decision-making and guide future research hypotheses.