Suggest Tests To Diagnose Stomach Pain In A Child

hello my 5 year old was tested via blood for celiac a year ago, it was negative. Stomach pains went away. Right before christmas they started again. We had more blood test, checked for every food allergy and celiac comprehensive. Two of the celiac comprehensive came back high and postive but two were neg. Her GI doctro is 90% it is celiac. He wants to do endoscopy. But is there any other genetic blood test before having to do endoscopy? Also, why can t we just go with his is 90% sure? Thanks Theresa