Prioritisation of Acute Appendicitis Using Appendistat Score

Detailed Description

Introduction Although conservative treatment for acute appendicitis may be appropriate in selected patients, appendicectomy remains the gold standard treatment of choice for acute appendicitis, as advocated by clinical guidelines (1,2). The timing of surgery is critical for improving patient outcomes. Guidelines from the National Confidential Inquiry into Patient Outcome and Death (NCEPOD) in the UK recommend prompt surgical intervention within hours of presentation (NCEPOD Category 2) (3). Evidence suggests that delays beyond 24 hours are associated with considerable safety concerns (4,5). Specifically, postponing surgical treatment beyond this timeframe can increase the likelihood of appendiceal perforation, necrosis, gangrene, and postoperative complications (6). Westfall and Charles demonstrated that the relative risk of perforation increases by 9% for each day of delayed treatment (7). However, challenges in emergency theatre capacity across NHS trusts frequently result in delays exceeding 24 hours, placing patients at risk of progression from uncomplicated to complicated appendicitis. A triaging tool capable of predicting patients at high risk of perforation is therefore required to ensure prioritization for timely surgical intervention.

The Appendistat (APS) scoring system was developed to identify patients at risk of complicated appendicitis. The score employs a logistic regression analysis of objective variables, including age, sex, white cell count (WCC), C-reactive protein (CRP), and bilirubin, to identify patients likely to develop complicated appendicitis (8). The APS score can be readily calculated during the initial assessment of patients suspected of acute appendicitis and can be integrated into electronic patient record (EPR) systems without the need to include symptoms, signs, or imaging results.

The purpose of this study was to assess the predictive value and clinical utility of the APS score in identifying patients at risk of complicated appendicitis on admission to a busy surgical emergency unit (SEU) at John Radcliffe Hospital, Oxford.

Methods

Design and Patients This was a retrospective chart review, cross-sectional observational diagnostic study with a single-gate design. A total of 592 patients undergoing appendicectomy at John Radcliffe Hospital, Oxford, between April 2023 and April 2024 were included. Patients were identified retrospectively from the EPR (Cerner Millennium within BT Local Service Provider [LSP]). Approval was obtained from the Trust Clinical Governance Department (reference 9210). Data were anonymized by two clinicians (TPJ and GK) and analysed by the senior investigator (ME), who was blinded to patient identifiers.

Inclusion criteria were: patients aged ≥16 years with a conclusive histological report of the appendix.

Exclusion criteria were: elective appendicectomy, appendicectomy performed as part of another procedure (e.g., hysterectomy), or absence of definitive histopathology.

Data Collection Data extracted included demographics, preoperative WCC, CRP, bilirubin, imaging reports, time from admission to surgery, intraoperative findings, operative duration, postoperative hospital stay, and final histology.

Outcome Groups

Histological diagnosis was used as the reference standard. Three categories were defined by consultant pathologists:

• Normal appendix: no inflammation.
• Acute uncomplicated appendicitis (AUA): suppurative/phlegmonous with transmural inflammation, ulceration, thrombosis, or intramural pus.
• Acute complicated appendicitis (ACA): gangrenous, perforated, or transmural inflammation with intramural/extramural pus.

1. Primary Outcome

• Title: Area under the ROC curve (AUC) of the Appendistat Score (APS) for predicting histologically confirmed complicated appendicitis.
• Description: Diagnostic accuracy of APS calculated using ROC and AUC analyses.
• Time Frame: At time of hospital admission (within 24 hours of presentation).
• Safety issue: No

1. Secondary Outcome 1

• Title: Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the Appendistat Score (APS) for detecting complicated appendicitis.
• Description: Diagnostic performance of APS compared with histology, expressed as sensitivity, specificity, PPV, and NPV at the defined cut-off point.
• Time Frame: At the time of hospital admission (within 24 hours of presentation).
• Safety issue: No

1. Secondary Outcome 2

• Title: Mean Appendistat Score (APS) values in patients with acute uncomplicated vs. complicated appendicitis
• Description: Comparison of mean APS values between patients with histologically confirmed acute uncomplicated appendicitis and those with acute complicated appendicitis.
• Time Frame: At time of hospital admission (within 24 hours of presentation)
• Safety Issue: No

Statistical analysis

Data were analysed using the Statistical Package for the Social Sciences (SPSS) version 23 and GraphPad Prism version 10. Continuous variables were analysed with the t-test, and categorical variables with the chi-square test. Receiver operating characteristic (ROC) curve and area under the curve (AUC) analyses were used to establish the diagnostic accuracy and determine the cut-off point of the APS score for ACA. The score was calculated using WCC, CRP, and bilirubin values at first presentation. A p-value of <0.05 was considered statistically significant.