Does colonoscopy cost covered by BCBSTX before annual deductible is met?

My GI specialist asked me to pay full cost for the colonoscopy because he said I met $0 out of this year's $500 deductible. The cost includes $330 (cash) plus facility fee and anesthesiologist fee. I will need to pay several hundred dollars for this year's colonoscopy. I had a routine colonoscopy done 6 years ago and two polyps were found and removed during the procedure. Is this year's colonoscopy considered to be a preventive or a diagnostic procedure? Please help me clarify this before I pay several hundreds out of my pocket.