A 58-year-old woman presents to the emergency department with acute right upper quadrant pain, fever (38.5°C), and leukocytosis (WBC 16,500/μL). On examination, the structure marked **D** in the diagram—deep tenderness reproduced when the examiner's fingers placed below the right costal margin encounter the inflamed gallbladder during the patient's inspiratory effort—is elicited. Which of the following best describes the clinical significance and diagnostic accuracy of this finding in acute cholecystitis?