Final answer:
The laboratory result that should prompt the nurse to contact the healthcare provider for a preoperative client is an elevated white blood cell count.
Step-by-step explanation:
The laboratory result for a preoperative client that should prompt the nurse to contact the healthcare provider is Option B: White blood cell (WBC) count: 85 x 109/L (8500/mm3). The normal range for white blood cell count is 3.5 to 11 x 109 cells/L, and a count of 85 x 109/L indicates a significantly elevated count, which may suggest an ongoing infection or other underlying health issue. The nurse should contact the healthcare provider for further evaluation and appropriate intervention.