The goal of the current study is to validate the LAPP score in a prospective multicenter validation study. Our hypothesis is that the application of the LAPP score leads to a reduction of 50% of negative appendectomies compared with a retrospective cohort in the same centers. The investigators have chosen to compare the negative appendectomy rate of this prospective multicenter validation study with a retrospective control group. The control group consists of 843 patients operated in 5 centers in 2008 and 2009 with a negative appendectomy rate of 9%.