Yes, my biopsy was positive. They performed the biopsy on the second day I was in the hospital for vision problems associated with the GCA. My vision turned out ok with treatment.

A negative biopsy doesn't necessarily mean you don't have GCA. The biopsy could have been from a section of the artery where there weren't any giant cells, or the biopsy could have been performed after the person had been taking prednisone for some time, and the prednisone caused the giant cells to shrink.