Slostad BD, et al. - The diagnostic accuracy of intraoperative surgical inspection and two-dimensional echocardiography vs a gold standard of pathological diagnosis in the cases of unicuspid aortic valve (UAV), by analyzing patients assigned a diagnosis of UAV by any technique in the Mayo Clinic echocardiographic database, tissue registry database, and electronic medical record. Using one or more method, a clinical diagnosis of UAV was applied to 380 patients. The clinical description given by transthoracic (TTE), transesophageal (TEE), or surgical inspection was compared with a pathologic evaluation in 196 (52%) cases. The sensitivity and specificity of these methods in diagnosing UAV were 15% and 87% for TTE, 28%, and 82% for TEE, and 52% and 51% for surgical inspection, respectively. All methods frequently led to misclassification of valves with bicuspid morphology and extensive commissural fusion as UAV. Owing to difficulties in accurately assigning a correct morphological diagnosis, intraoperative surgical inspection and echocardiography had limitations for diagnosing UAV. This was indicative of possible inaccuracy of the current understanding of the natural history of UAV.