Background: Appendicitis is one of the most causes of emergency abdominal surgery worldwide and its diagnosis has been a clinical challenge so far. This study was conducted to estimate positive and negative predictive values, sensitivity and specificity of some of the signs and symptoms alongside several lab results. Methods: This study had a prospective design that was performed by the completion of a questionnaire via 207 patients who were suspicious of appendicitis. Results: Among 207 patients, 126 (60. 9%) were male and 81 (39. 1%) were female. Appendicitis were approved in 178(86%) and rejected in 29(14%) based on pathology results. Rejected cases of appendicitis were more in females (22. 2%) compared to males (8. 7%). The mean for age was 26. 55 years old, with an interquartile range of 19 to 32. Sensitivity, specificity, positive and negative predictive values for significant results were as follows, respectively: dysuria 2. 8%, 100%, 100%, 14. 4%, diarrhea 1. 7%, 100%, 100%, 14. 2%, fever 5. 1%, 100%, 100%, 14. 6%, abdominal rigidity 3. 4%, 100%, 100%, 14. 4%, active urine analysis 11. 7%, 86. 2%, 83. 3%, 14. 2%, 1+ C-reactive protein(CRP) 76. 3%, 48. 3%, 90%, 4+ CRP 2. 8%, 96. 6%, 83. 3%, 14%. Conclusion: Based on the results of this study, fever, dysuria, diarrhea, abdominal rigidity and urine analysis had significant specificity and positive predictive value, therefore they can be helpful in the diagnosis of acute appendicitis in parallel with other signs, symptoms and lab results, although their absence cannot rule out this diagnosis.