University of Leuven and University of Hasselt 1 article published in JoVE Medicine Rectal Organoid Morphology Analysis (ROMA): A Diagnostic Assay in Cystic Fibrosis Senne Cuyx1,2, Anabela S. Ramalho1, Nikky Corthout3,4, Steffen Fieuws5, Eva Fürstová6, Kaline Arnauts7,8, Marc Ferrante7,9, Catherine Verfaillie8, Sebastian Munck3,4, Mieke Boon1,2, Marijke Proesmans1,2, Lieven Dupont10,11, Kris De Boeck1,2, François Vermeulen1,2 1Department of Development and Regeneration, Woman and Child Unit, CF research lab, KU Leuven, 2Department of Pediatrics, Pediatric Pulmonology, University Hospitals Leuven, 3VIB Bio Imaging Core, VIB-KU Leuven Center for Brain & Disease Research, 4Department for Neuroscience, KU Leuven, 5Interuniversity Center for Biostatistics and Statistical Bioinformatics, University of Leuven and University of Hasselt, 6Department of Pediatrics, 2nd Faculty of Medicine, Charles University and Motol University Hospital, 7Department of Chronic Diseases and Metabolism (CHROMETA), Translational Research Center for Gastrointestinal Disorders (TARGID), KU Leuven, 8Department of Development and Regeneration, Stem Cell Institute Leuven (SCIL), KU Leuven, 9Department of Gastroenterology and Hepatology, University Hospitals Leuven, KU Leuven, 10Department of Chronic Diseases, Metabolism and Ageing; Pneumology, KU Leuven, 11Department of Respiratory Diseases, University Hospitals Leuven This protocol describes rectal organoid morphology analysis (ROMA), a novel diagnostic assay for cystic fibrosis (CF). Morphological characteristics, namely the roundness (circularity index, CI) and the presence of a lumen (intensity ratio, IR), are a measure of CFTR function. Analysis of 189 subjects showed perfect discrimination between CF and non-CF.