Bruce is already reaching for a clean syringe to get a blood sample. "Well, maybe not for a cure, but at least something to slow it down." His mind's already trying to turn over ideas on what could be done.
He hesitates before putting on the tourniquet. "...if you don't find a cure?" It was one thing if Bruce didn't find a cure for himself. It was another to try and cure this before it killed Tony.