The effectiveness of emergency surgery vs. non-emergency surgery strategies for emergency admissions with acute appendicitis, gallstone disease, diverticular disease, abdominal wall hernia or intestinal obstruction is unknown. Data on emergency admissions for adult patients from 2010 to 2019 at 175 acute National Health Service hospitals in England were extracted from the Hospital Episode Statistics database. Cohort sizes were: 268,144 (appendicitis); 240,977 (gallstone disease); 138,869 (diverticular disease); 106,432 (hernia); and 133,073 (intestinal obstruction). The primary outcome was number of days alive and out of hospital at 90 days. The effectiveness of emergency surgery vs. non-emergency surgery strategies was estimated using an instrumental variable design and is reported for the cohort and pre-specified sub-groups (age, sex, number of comorbidities and frailty level). Average days alive and out of hospital at 90 days for all five cohorts were similar, with the following mean differences (95%CI) for emergency surgery minus non-emergency surgery after adjusting for confounding: À0.73 days (À2.10-0.64) for appendicitis; 0.60 (À0.10-1.30) for gallstone disease; À2.66 (À15.7-10.4) for diverticular disease; À0.07 (À2.40-2.25) for hernia; and 3.32 (À3.13-9.76) for intestinal obstruction. For patients with 'severe frailty', mean differences (95%CI) in days alive and out of hospital for emergency surgery were lower than for non-emergency surgery strategies: À21.0 (À27.4 to À14.6) for appendicitis; À5.72 (À11.3 to À0.2) for gallstone disease, À38.9 (À63.3 to À14.6) for diverticular disease; À19.5 (À26.6 to À12.3) for hernia; and À 34.5 (À46.7 to À22.4) for intestinal obstruction. For patients without frailty, the mean differences (95%CI) in days alive and out of hospital were: À0.18 (À1.56-1.20) for appendicitis; 0.93 (0.48-1.39) for gallstone disease; 5.35 (À2.56-13.28) for diverticular disease; 2.26 (0.37-4.15) for hernia; and 18.2 (14.8-22.47) for intestinal obstruction. Emergency surgery and non-emergency surgery strategies led to similar average days alive and out of hospital at 90 days for five acute conditions. The comparative effectiveness of emergency surgery and non-emergency surgery strategies for these conditions may be modified by patient factors.

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.

Background This paper assesses variation in rates of emergency surgery (ES) amongst emergency admissions to hospital in patients with acute appendicitis, cholelithiasis, diverticular disease, abdominal wall hernia, and intestinal obstruction. Methods Records of emergency admissions between 1 April 2010 and 31 December 2019 for the five conditions were extracted from Hospital Episode Statistics for 136 acute National Health Service (NHS) trusts in England. Patients who had ES were identified using Office of Population Censuses and Surveys (OPCS) procedure codes, selected by consensus of a clinical panel. The differences in ES rates according to patient characteristics, and unexplained variations across NHS trusts were estimated by multilevel logistic regression, adjusting for year of emergency admission, age, sex, ethnicity, diagnostic subcategories, index of multiple deprivation, number of co-morbidities, and frailty. Results The cohort sizes ranged from 107 325 (hernia) to 268 253 (appendicitis) patients, and the proportion of patients who received ES from 11.0 per cent (diverticular disease) to 92.3 per cent (appendicitis). Older patients were generally less likely to receive ES, with adjusted odds ratios (ORs) of ES for those aged 75–79 versus those aged 45–49 years: 0.34 (appendicitis), 0.49 (cholelithiasis), 0.87 (hernia), and 0.91 (intestinal obstruction). Patients with diverticular disease aged 75–79 were more likely to receive ES than those aged 45–49 (OR 1.40). Variation in ES rates across NHS trusts remained after case mix adjustment and was greatest for cholelithiasis (trust median 18 per cent, 10th to 90th centile 7–35 per cent). Conclusion For patients presenting as emergency hospital admissions with common acute conditions, variation in ES rates between NHS trusts remained after adjustment for demographic and clinical characteristics. Age was strongly associated with the likelihood of ES receipt for some procedures.

The personalization of treatment choice can be informed by comparative effectiveness research that exploits the widespread availability of electronic health records (EHRs), but requires methods that address confounding and heterogeneity. For conventional linear Instrumental Variable (IV) methods, such as two-stage least squares (2SLS) to identify policy-relevant estimands such as the Average Treatment Effect (ATE) or Conditional Average Treatment Effects (CATEs), it is required that there is no essential heterogeneity (Heckman et al., 2006). Essential heterogeneity arises when treatment effects differ over levels of unmeasured confounders, in which case 2SLS no longer identifies the ATE, even if the instrument is strong and valid (Heckman

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