Dear Editor-in-Chief,


      Practical exams are frequently used in the training and evaluation of medical students. One such exam is the Objective Structured Clinical Examination (OSCE). The OSCE exam is organized objectively in different stations, and examinees are asked to perform specific clinical tasks at each station (1). One limitation of the OSCE exam is its high implementation cost (2). Increasing the number of OSCE stations reduces measurement error and enhances test reliability (3). Conversely, reducing station numbers can help save resources like examiners, patients, or standardized patients (SPs) (4). The sequential OSCE method has been proposed to address cost challenges while maintaining high reliability (5). In this approach, students first participate in a preliminary test with fewer stations. For instance, if the main test typically involves 20 stations, the initial test might include only 10 or fewer stations. By reducing the number of stations, patients, SPs, and examiners, the sequential OSCE method significantly lowers examination costs. Students who do not pass the initial test will participate in a supplemental test, with their total performance across both tests determining their final status (3, 4), equivalent to participating in a single comprehensive exam. Students who successfully pass the initial exam are exempted from the subsequent test, with only their first exam performance being considered (4).
In sequential assessment, the results of the first test should accurately predict students' performance in the main test, effectively screening capable learners. Achieving this requires careful consideration of several key points: designing the entire test's blueprint first and then strategically selecting stations for the initial screening test. The screening test must be conceptualized within the comprehensive test's framework and context. Understanding the typical failure rate is crucial, as most similar examinations expect only a small number of students to fail. The screening test should be meticulously designed to minimize both false negatives and false positives (6). False positives occur when students pass the screening exam but are ultimately rejected in the total exam, indicating potential decision-making errors and low test specificity. Since OSCE assesses clinical competence, incorrectly accepting an incompetent student poses a serious threat to patient safety. False negatives represent students who initially fail the test but demonstrate acceptable performance across both tests and are ultimately passed. The number of negative cases is critical: a small number suggests an economical second test, while a large number undermines the primary goal of resource conservation. Ideally, both false positives and false negatives should be minimized, with a particular emphasis on maintaining low false positive rates in the screening test (6, 7).