169 Classifying study participants in clinical trials Background Valid and reliable classification of the clinical diagnosis of study participants is a prerequisite for the evaluation of new and existing imaging strategies. To conduct such studies, ideally a single reference standard evaluation is available for disease classification [1]. If such a reference standard evaluation is not available, alternative classification methods include the use of a clinical reference standard, such as a panelbased diagnosis [2]. Relying on an expert panel of medical specialists who retrospectively evaluate the available test results and additional findings to classify study participants in a consensus procedure, is regarded an acceptable approach [3]. Unfortunately, classification by medical specialists of large numbers of patients is often not feasible, due to budget and manpower restraints. To obtain a valid and cost-efficient classification of patients suspected of pulmonary disease, we developed a structured approach that involves medical students, residents, an expert panel, and a detailed handbook. We developed diagnostic guidelines that combine multiple test results via predefined deterministic rules. We evaluated this diagnostic handbook in a diagnostic study on chest imaging. The OPTIMACT trial (OPTimal IMAging strategy in patients suspected of non-traumatic pulmonary disease at the ED: chest X–ray or ultra-low-dose (ULD) chest CT) is designed to evaluate the effectiveness of replacing chest x-ray for ULD chest CT in the diagnostic work-up of patients suspected of non-traumatic pulmonary disease at the emergency department (ED) [4]. We hypothesised that our structured approach using a carefully developed reference standard for diagnostic classification would be efficient, and that such classification by a team of medical students, residents and an expert panel would be valid. Methods Subjects This study was performed within the framework of the OPTIMACT randomised controlled trial (RCT). Specifics of the study protocol can be found elsewhere [4]. Briefly, the OPTIMACT trial is a multicentre, pragmatic RCT with a non-inferiority design to evaluate the effectiveness of replacing chest x-ray for ULD chest CT in the diagnostic work-up of patients suspected of non-traumatic pulmonary disease at the ED. For the evaluation of our classification strategy, we took a stratified, random subset of 240 OPTIMACT participants (10%), using a random number generator. The size of this subset was based on comparable evaluations performed earlier [5]. We ensured a 1:1 ratio of chest x-ray versus ULD chest CT (120/120) and a 2:1 ratio of participants enrolled at the two participating hospitals (160/80), matching the distribution in the OPTIMACT cohort. Diagnostic handbook The research team, consisting of a chest radiologist, an internist, a pulmonologist and a cardiologist, carefully developed a handbook consisting of diagnostic classification rules (Supplementary material 1). We defined 26 thoracic diagnostic labels for adults suspected of non-traumatic pulmonary disease at the ED. These diagnostic labels can be divided into five diagnostic categories: respiratory tract infections, other pulmonary diseases, heart diseases, vascular diseases, nodules and tumours. Each diagnostic label 8
RkJQdWJsaXNoZXIy MTk4NDMw