Diagnosing Crohn's

My husband has been sick off and on, the doctors are ruling out Crohns...however he's had an EGD, colonoscopy, CT with and wo contrast, ultrasound and hydascan, barium swallow, stool test and blood work with no answers besides unexplained gastritis (neg for h-pylori which is most common cause of gastriris). We have an appt at the Mayo Clinic on March 1st in Jacksonville....however we are concerned that if he is not having symptoms during that time will they still be able to diagnose him?