Patient Safety & Quality Improvement USMLE Step 1 Practice Question

A 55-year-old woman with no significant past medical history presents to the emergency department with acute right lower quadrant pain, fever, and elevated WBC. CT imaging confirms acute appendicitis, and she is scheduled for an emergent laparoscopic appendectomy. The surgical team implements a standardized WHO surgical safety checklist that includes: (1) pre-operative team briefing with patient identity and procedure verification, (2) surgical site marking by the surgeon, and (3) a formal time-out pause immediately before incision where all team members confirm patient identity, procedure, and site. Multiple high-quality studies have demonstrated that systematic implementation of this checklist significantly improves patient outcomes. Which of the following metrics would best evaluate whether this intervention is achieving its intended effect on reducing patient harm?