A 42-year-old woman from Delhi presents with a 3-month history of progressive dyspnea and fatigue. Clinical examination reveals a diastolic murmur at the apex. Transthoracic echocardiography is performed to assess for mitral stenosis. The echocardiographic findings are compared against cardiac catheterization (gold standard). In the study population of 200 patients: - True positives (echo positive, catheter positive): 45 - False positives (echo positive, catheter negative): 15 - True negatives (echo negative, catheter negative): 120 - False negatives (echo negative, catheter positive): 20 What is the sensitivity of transthoracic echocardiography for detecting mitral stenosis in this cohort?