Blood Testing For A Toddler

[LJ-Mom]

My son was off gluten for almost a month and we saw little if any improvement. We'd removed gluten, egg, dairy, fruit and were still getting daily diarrhea with only 2 solid poops over 4 weeks. My son is also teething (8 teeth since mid-Dec), so not sure if that is confounding. Have put back gluten, still messy diarrhea but it is actually back to being brown and not so stinky vs. green/yellow and horrible after removing gluten, dairy and fruit.

We're due to go in for blood tests for allergy, celiac and other issues soon. I want to make sure if it is celiac (with several other allergies/intolerences) that I have the best chance for a postive test for antibodies. How long should the gluten be back in the diet for positive results?

I know some will say it doesn't matter about the blood test result, but we're not seeing improvements so I 'm looking for minimum length of time to have gluten in system. Also how much per day must I give? Is one piece of bread and some cheerios sufficient?