eprintid: 10149923 rev_number: 7 eprint_status: archive userid: 699 dir: disk0/10/14/99/23 datestamp: 2022-06-09 13:46:43 lastmod: 2022-06-09 13:46:43 status_changed: 2022-06-09 13:46:43 type: article metadata_visibility: show sword_depositor: 699 creators_name: Moler-Zapata, Silvia creators_name: Grieve, Richard creators_name: Lugo-Palacios, David creators_name: Hutchings, A creators_name: Silverwood, R creators_name: Keele, Luke creators_name: Kircheis, Tommaso creators_name: Cromwell, David creators_name: Smart, Neil creators_name: Hinchliffe, Robert creators_name: O'Neill, Stephen title: Local Instrumental Variable Methods to Address Confounding and Heterogeneity when Using Electronic Health Records: An Application to Emergency Surgery ispublished: inpress divisions: B14 divisions: J81 divisions: B16 divisions: UCL keywords: cost-effectiveness analysis, emergency surgery, heterogeneous treatment effects, instrumental variable, personalized medicine note: This article is distributed under the terms of the Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by/4.0/) which permits any use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage). abstract: BACKGROUND: Electronic health records (EHRs) offer opportunities for comparative effectiveness research to inform decision making. However, to provide useful evidence, these studies must address confounding and treatment effect heterogeneity according to unmeasured prognostic factors. Local instrumental variable (LIV) methods can help studies address these challenges, but have yet to be applied to EHR data. This article critically examines a LIV approach to evaluate the cost-effectiveness of emergency surgery (ES) for common acute conditions from EHRs. METHODS: This article uses hospital episodes statistics (HES) data for emergency hospital admissions with acute appendicitis, diverticular disease, and abdominal wall hernia to 175 acute hospitals in England from 2010 to 2019. For each emergency admission, the instrumental variable for ES receipt was each hospital's ES rate in the year preceding the emergency admission. The LIV approach provided individual-level estimates of the incremental quality-adjusted life-years, costs and net monetary benefit of ES, which were aggregated to the overall population and subpopulations of interest, and contrasted with those from traditional IV and risk-adjustment approaches. RESULTS: The study included 268,144 (appendicitis), 138,869 (diverticular disease), and 106,432 (hernia) patients. The instrument was found to be strong and to minimize covariate imbalance. For diverticular disease, the results differed by method; although the traditional approaches reported that, overall, ES was not cost-effective, the LIV approach reported that ES was cost-effective but with wide statistical uncertainty. For all 3 conditions, the LIV approach found heterogeneity in the cost-effectiveness estimates across population subgroups: in particular, ES was not cost-effective for patients with severe levels of frailty. CONCLUSIONS: EHRs can be combined with LIV methods to provide evidence on the cost-effectiveness of routinely provided interventions, while fully recognizing heterogeneity. HIGHLIGHTS: This article addresses the confounding and heterogeneity that arise when assessing the comparative effectiveness from electronic health records (EHR) data, by applying a local instrumental variable (LIV) approach to evaluate the cost-effectiveness of emergency surgery (ES) versus alternative strategies, for patients with common acute conditions (appendicitis, diverticular disease, and abdominal wall hernia).The instrumental variable, the hospital's tendency to operate, was found to be strongly associated with ES receipt and to minimize imbalances in baseline characteristics between the comparison groups.The LIV approach found that, for each condition, there was heterogeneity in the estimates of cost-effectiveness according to baseline characteristics.The study illustrates how an LIV approach can be applied to EHR data to provide cost-effectiveness estimates that recognize heterogeneity and can be used to inform decision making as well as to generate hypotheses for further research. date: 2022-05-24 date_type: published publisher: SAGE Publications official_url: https://doi.org/10.1177/0272989X221100799 oa_status: green full_text_type: pub language: eng primo: open primo_central: open_green verified: verified_manual elements_id: 1959103 doi: 10.1177/0272989X221100799 medium: Print-Electronic lyricists_name: Silverwood, Richard lyricists_id: RSILV59 actors_name: Bracey, Alan actors_id: ABBRA90 actors_role: owner full_text_status: public publication: Medical Decision Making event_location: United States issn: 0272-989X citation: Moler-Zapata, Silvia; Grieve, Richard; Lugo-Palacios, David; Hutchings, A; Silverwood, R; Keele, Luke; Kircheis, Tommaso; ... O'Neill, Stephen; + view all <#> Moler-Zapata, Silvia; Grieve, Richard; Lugo-Palacios, David; Hutchings, A; Silverwood, R; Keele, Luke; Kircheis, Tommaso; Cromwell, David; Smart, Neil; Hinchliffe, Robert; O'Neill, Stephen; - view fewer <#> (2022) Local Instrumental Variable Methods to Address Confounding and Heterogeneity when Using Electronic Health Records: An Application to Emergency Surgery. Medical Decision Making 10.1177/0272989X221100799 <https://doi.org/10.1177/0272989X221100799>. (In press). Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/10149923/1/0272989x221100799-2.pdf