PA Celiac Mom

Does this sound like celiac? My son has had diarrhea and vomiting (about 1x/day) for the last 4 weeks. We thought it was from the cold virus that turned into an ear infection and later bronchitis. Once the virus cleared up, the d & v continued. The pediatrician ran a stool sample, positive for the tissue transglutaminate = 5. But negative for the other...

How do you know if an item was produced on equipment or just in the same facility? Does the packaging specify? What if the facility changes their routine, how will you know?