External validation of the Surgical Outcome Risk Tool (SORT) in 3305 abdominal surgery patients in the independent sector in the UK

K Oakland,S Dorudi,D Walker,C Bucknall,T Cross,D Cosentino

doi:10.1186/s13741-020-00173-1

Abstract

BackgroundAssessing the risk of post-surgical mortality is a key component of pre-surgical planning. The Surgical Outcome Risk Tool (SORT) uses pre-operative variables to predict 30-day mortality. The aim of this study was to externally validate SORT in patients undergoing major abdominal surgery.MethodsData were collected from patients treated in five independent hospitals in the UK. Individualised SORT scores were calculated, and area under the receiver operating characteristic (AUROC) and precision-recall curves (PRC) plus 95% confidence intervals (CI) were drawn to test the ability of SORT to identify in-hospital death. Outcomes of patients with a SORT predicted risk of mortality of ≥ 5% (high risk) were compared to those with a predicted risk of < 5% (standard risk).ResultsThe study population comprised 3305 patients, mean age 51 years, 2783 (84.2%) underwent elective surgery most frequently involving the colon (24.6%), or liver, pancreas or gallbladder (18.2%). Overall, 1551 (46.9%) patients were admitted to ICU and 29 (0.88%) died. The AUROC of SORT for discriminating patients at risk of death in hospital was 0.899 (95% CI 0.849 to 0.949) and the PRC 0.247. In total, 72 (2.18%) patients were stratified as high risk. There were more unplanned ICU admissions and deaths in this group compared to the standard risk group (25.0% and 3.3%, versus 3.1% and 0.5%, respectively).ConclusionWe externally validated SORT in a large population of abdominal surgery patients. SORT performed well in patients with lower risk profiles, but underpredicted adverse outcomes in the higher risk group.

Highlights

In 2010, the National Confidential Enquiry into Patient Outcome and Death (NCEPOD) conducted a national review of care provided to high-risk surgical patients
A key finding was the need for a United Kingdom (UK)-wide system that could reliably identify patients at high risk of mortality and morbidity (National Confidential Enquiry into Patient Outcomes and Death, 2011)
The RCS recommended that high-risk surgical patients, defined as those with a predicted mortality of ≥ 5%, should receive timely surgery in the presence of a consultant surgeon and should immediately be admitted to critical care post-operatively (Royal College of Surgeons of England, 2018)

Summary

Introduction

In 2010, the National Confidential Enquiry into Patient Outcome and Death (NCEPOD) conducted a national review of care provided to high-risk surgical patients. The Surgical Outcome Risk Tool (SORT) was developed from a population of 16,788 patients who underwent elective or emergency general, head and neck, ophthalmology, orthopaedic, thoracic, urology or vascular surgery with the aim of predicting 30-day mortality following surgery (Protopapa et al, 2014) but as yet has not been fully externally validated. It comprises procedure code, operation severity, American Society of Anaesthesiologists’ physical status classification (ASA), clinical urgency, surgical site (thoracic, gastrointestinal or vascular surgery), cancer (active malignancy within the last 5 years) and age, all of which are available preoperatively. The aim of this study was to externally validate SORT in patients undergoing major abdominal surgery

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