Prospective Validation of the APPEND Clinical Prediction Rule for Appendicitis: A Cohort Study

Right iliac fossa (RIF) pain is a common referral to general surgery as acute appendicitis is one of the most common underlying diagnoses. The clinical diagnosis of appendicitis continues to challenge clinicians. Clinical prediction rules (CPRs) are one method used to improve diagnostic accuracy and reduce negative appendicectomy rates. The APPEND score is a novel CPR that was developed at Middlemore Hospital.

To prospectively evaluate the performance of the APPEND CPR within a pathway dedicated to the management of RIF pain.

A comparative cohort study of the clinical pathway incorporating the APPEND CPR pain was performed from January to July 2016. This was compared to the retrospective cohort used to develop the APPEND CPR. The primary end point was negative appendicectomy rate.

The negative appendicectomy rate in the prospective cohort was 9.2% (95% CI: 5.3%, 13.2%) compared to 19.8% (CI 16.2, 23.4%) in the retrospective cohort that did not use the APPEND CPR. After adjusting for multiple variables, the odds ratio of a negative appendicectomy was 2.33 times higher (95% CI; 1.26, 4.3, P value 0.007) in the retrospective cohort compared to the prospective cohort. An APPEND score of ≥5 was 87 % specific for ruling in appendicitis (PPV 94%) and a score of ≥1 was 100% sensitive in ruling out appendicitis (NPV 100%).

In a comparative cohort study of an RIF pain pathway incorporating the APPEND CPR, the rate of negative appendicectomy showed a significant reduction by more than 50%.