Comparing Proposed Algorithm and Current Practice in the Evaluation of Suspected Appendicitis

Acute appendicitis is one of the most common causes of acute abdominal pain requiring surgical intervention, with a lifetime risk of 8.6% for males and 6.7% for females. Historically, negative appendectomy rates of more than 20% were considered the norm. This is no longer acceptable in the current era, as despite low complication rates in the setting of negative appendectomy, conditions such as incisional hernias, intestinal obstruction secondary to adhesions and stump leakages can still result in significant morbidity.

Computed Tomography (CT) scan has emerged as the dominant imaging modality for evaluation of suspected appendicitis in adults. It has decreased negative appendectomy rates to fewer than 10%. However, the radiation exposure with CT poses a concern, particularly in appendicitis, which occurs predominantly in young patients most susceptible to the adverse effects of radiation. Available literature has estimated that at least 25% of CT scans are not clinically warranted and may pose more harm than benefits. Rules for clinical decision guiding CT utilization is thus essential to minimize unnecessary CT scans, which not only poses a radiation risk but also contributes to increased healthcare costs.

Currently, the management of suspected appendicitis is surgeon dependent. Accuracy of diagnosis is dependent on individual's clinical acumen, preference for CT scan and threshold for offering surgery. There is also a recent trend towards indiscriminate CT utilization with an estimated 1 in 4 CT scans ordered found to be clinically unwarranted. The Alvarado Score (AS) is a 10 point clinical scoring system for acute appendicitis that has been extensively validated. AS on a prospective database of 500 consecutive cases of suspected appendicitis admitted to Singapore General Hospital, Department of General Surgery from August 2013 to July 2014, was validated. A comparison was then made between diagnostic performance measures of CT scan and AS to identify ranges of AS where patients are unlikely to benefit from CT evaluation. From these findings, an objective algorithm for the management of suspected appendicitis guided by AS was formulated. Ideally, the algorithm will streamline CT utilization and reduce the number of CT scans ordered with an acceptable negative appendectomy rate. Thus, investigators hope to validate this proposed algorithm through a randomized control trial.

The trial will recruit 160 eligible patients over 2 years. Eligible patients who consented to participate in the trial will be subjected to randomization into one of the two trial groups - Usual Care Arm or Intervention Arm - in equal numbers (n=80). Patients randomized to Usual Care Arm will be managed according to individual's doctor discretion. On the other hand, patients randomized to Intervention Arm will have their Alvarado Score tabulated and managed as per proposed algorithm.

The primary objective of the trial is to show that the proposed management algorithm is effective in reducing the percentage of CT utilization as compared to current best practice for patients with suspected appendicitis seen at Singapore General Hospital and Sengkang Health. The hypothesis is that the proposed management algorithm will reduce the percentage of CT scans from 80%, which is the CT utilization rate when current best practice is used, to 60%. The study will be powered to detect this decrease with a 5% type I error rate.

The secondary objective of the trial is to estimate the proportion of negative appendectomy and missed diagnosis in each of the study arm. In addition, the total length of stay in days and overall cost of stay would also be estimated and compared between the two study arms. These secondary objectives are purely descriptive and no hypothesis testing is planned for these objectives.

Randomization schedule will be generated using standard statistical software by a statistician who is not going to be involved in data analysis. Envelopes containing the treatment instructions will be marked according to that schedule. Randomization will be performed in blocks of six subjects, three for intervention and three for control arm, to ensure balanced groups.

If the proposed algorithm is validated and found to be of value, it can potentially be implemented nationwide as a standard protocol for the evaluation of suspected appendicitis. This may reduce the number of unwarranted CT scans performed and reduce health care costs. In addition, the reduction of unnecessary CT scans helps to minimize unwarranted radiation exposure which is not insignificant. A single CT Abdomen Pelvis for evaluation of suspected appendicitis exposes one to 14 mSv of ionizing radiation which adds an additional cancer risk of up to 0.2% for an individual who is 30 years of age. The cumulative effects of such radiation exposure may prove significant and a management algorithm guiding sensible CT utilization will help ease the burden of radiation induced complications in the future.