Diagnosing acute appendicitis in children is still a challenge even for experienced clinicians. Failure to recognize this acute condition can result in perforation, with consequent peritonitis, or misdiagnosis can result in negative appendectomies. C-reactive protein in blood can be elavated in children with acute appendicitis. The aim of this research is to compare the diagnostic value of C-reactive protein from the blood and saliva of children with acute appendicitis and to prove wheter the analysis of biomarker from saliva as a minimally invasive procedure can be sufficient for diagnosis.

Inclusion Criteria:

• children with age from 5 to 17 with acute abdominal pain
• children with clinical signs of appendicitis

Exclusion Criteria:

• previous diagnosis of chronic and/or malignant disease
• children wich had previous abdominal surgery
• pregnancy

Patients from 5 to 17 years of age, presenting with acute abdominal pain consistent with diagnosis of acute appendicitis, to Emergency Surgery Department at the University Hospital Split