Development of the RIPASA score: a new appendicitis scoring system for the diagnosis of acute appendicitis.

INTRODUCTION Acute appendicitis is one of the most common surgical emergencies. The Alvarado and modified Alvarado scores have been developed to aid diagnosis, but both scoring systems have poor sensitivity and specificity when applied in Middle Eastern and Asian populations. The aim of this study was to develop a new scoring system that is suitable for the local population. METHODS Clinical data from 312 patients who had undergone an emergency appendicectomy was retrospectively collected and used to generate 15 parameters. The probability was calculated and a score of 0.5, 1.0 or 2.0 was allocated to each parameter. The receiver operating curve (ROC), sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the new scoring system were derived using the StatsDirect statistical software. RESULTS The 15 parameters and the scores generated were age (less than 40 years is 1 point; greater than 40 years is 0.5 point), gender (male is 1 point; female is 0.5 point), right iliac fossa (RIF) pain (0.5 point), migration of pain to RIF (0.5 point), nausea and vomiting (1 point), anorexia (1 point), duration of symptoms (less than 48 hours is 1 point; more than 48 hours is 0.5 point), RIF tenderness (1 point), guarding (2 points), rebound tenderness (1 point), Rovsing's sign (2 points), fever (1 point), raised white cell count (1 point), negative urinalysis (1 point) and foreign national registration identity card (1 point). The optimal cut-off threshold score from the ROC was 7.5, with a sensitivity of 88 percent, a specificity of 67 percent, a PPV of 93 percent and an NPV of 53 percent. The negative appendicectomy rate decreased significantly from 16.3 percent to 6.9 percent, which was a 9.4 percent reduction (p is 0.0007). CONCLUSION The new appendicitis scoring system looked promising when applied to our settings, and had a better sensitivity and specificity than the Alvarado score when applied to Asian populations. A significant reduction in the negative appendicectomy rate was also predicted. A prospective evaluation of this new appendicitis scoring system, referred to as the RIPASA score, is ongoing.