If a blood and urine test is performed to check for appendicits and tests come back good. does this mean you're in the clear and don't have it?

Not always: Urine test would exclude urinary infection as etiology for pain. Blood tests would show elevation of inflammatory markers and white blood cell count to incriminate infectious inflammatory process. Gold standard now ultrasound if normal appendix visualized. Some times not visualized on Ultrasound, then CT of abdomen with intravenous contrast usually has answer of appendix or other etiology

Appendicitis: The surest way to diagnose appendicitis is by history, clinical examination, and CT abdomen. If you are pain free you are not likely to have appendicitis.

NO: Second most definitive test is non-contrast CT of the abdomen. Laproscopy is the most definative