Epidemiology & Prevention USMLE Step 1 Practice Question

A 59-year-old woman with hypertension (BP 148/92 mmHg) and hyperlipidemia presents for routine evaluation. She is asymptomatic with normal vital signs otherwise (HR 78/min, RR 16/min, Temp 37°C, SpO2 98%). Recent labs show LDL 156 mg/dL and normal fasting glucose. She takes lisinopril but denies chest pain or dyspnea. She asks which health measure best detects disease at an early, treatable stage rather than preventing initial occurrence. Which intervention exemplifies secondary prevention?