BACKGROUND: Although many clinical prediction rules (CPRs) for appendicitis 
exist, none have been developed for a New Zealand population presenting with 
right iliac fossa (RIF) pain. The aim of this study was to derive and validate 
an appendicitis CPR for our population.
METHOD: This is a retrospective review of all patients from December 2010 to 
February 2012 of at least 15 years of age presenting to the general surgery 
service with RIF pain. Patient data were divided into derivation and validation 
groups. Univariate and multiple regression analyses identified significant 
predictors of appendicitis which were used to construct a CPR. A retrospective 
validation study was then performed and the CPR was refined accordingly. 
Finally, the accuracy of the CPR was tested.
RESULTS: The final components of the new CPR, the APPEND score, were Anorexia, 
migratory Pain, local Peritonism, Elevated C-reactive protein, Neutrophilia and 
male gender (Dude). This CPR has an area under the receiver operating 
characteristic curve of 0.84. The CPR can stratify patients into low, 
intermediate and high-risk groups which may standardize patient care and reduce 
the negative appendicectomy rate.
CONCLUSION: A new CPR for predicting appendicitis, in patients presenting with 
RIF pain, has been derived and validated for use in our population. A 
prospective study to further evaluate its performance is required.