Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn

1. Royal College of Surgeons in IrelandColáiste Ríoga na Máinleá in Éirinn A Systematic Review and Meta-Analysis of the Alvarado Score in Predicting Acute Appendicitis Robert Ohle, Fran O’Reilly, Kirsty O’Brien, Tom Fahey and Borislav D Dimitrov

2. Overview • Introduction • Methods • Results • Discrimination analysis • Calibration analysis • Discussion • Summary and implications

3. Introduction

4. Background • Acute appendicitis is the most common cause of an acute abdomen requiring surgery - lifetime risk ~ 7% • Difficult diagnosis - symptoms of appendicitis overlap with a number of other conditions making diagnosis a challenge • Imaging can be useful, but expensive and not always available

5. Clinical Prediction Rules • Clinical tool used to stratify patients according to their probability of having a target disorder or outcome of interest. • CPRs quantify the contribution of: • History • Examination • Diagnostic tests • Outcome of interest can be in terms of diagnosis, prognosis, referral or treatment

6. Alvarado score 1-4 5-6 7-10 Discharge Observation Surgery

7. Methods

8. Inclusion/exclusion criteria • Population • Emergency department/surgical ward • Signs and symptoms suggestive of appendicitis • Study type • prospective and retrospective studies • No Restrictions imposed for: • age, sex or size of study population • language or publication status

9. Outcome measures and quality assessment • Outcome measures and reference standards • Histological examination • Follow up • No repeat admissions • Quality assessment – QUADAS

10. Statistical methods • Discrimination analysis (Diagnostic test accuracy) • Admission, 1-4 compared to 5-10 • Surgery, 1-6 compared to 7-10 • Sensitivity, specificity +/- likelihood ratios • STATA 9.1 metandi • Calibration analysis • The derived (index) rule was used as a predictive model and applied to all validation studies • Pooled results are presented as risk ratios (RRs) with 95% confidence interval • Subgroup analysis on men, woman and children

11. Results

12. Quality of included studies • Quality of studies was good for most items • However, many studies did not actively follow up patients who had a low score and were discharged

13. Discrimination analysis

14. Calibration

15. Low Risk (1-4)

16. Intermediate Risk (5-6)

17. High Risk (7-10)

18. Discussion

19. Clinical Pathway Alvarado Score 1-4 5-6 7-10 Discharge CT Surgical consult

20. Summary and implications • It is a sensitive criteria for admission • As the sole criteria for surgery, could lead to a high number of negative appendectomies • Accurately predicts appendicitis in men of all risk strata • Consistently over predicts in women of all risk strata • Produces inconsistent results in children • Potential clinical impact especially in low resource settings • Users should be aware of its limitations in certain patient groups

21. Acknowledgements • Robert Ohle and Fran O’Reilly • The HRB Centre for Primary Care Research • The Health Research Board of Ireland for funding