In the European Union (EU) legislative framework for orphan medicinal product designation, establishing that a condition affects not more than five in 10,000 people is a prerequisite for applications based on rarity. Demonstrating this requirement to the Committee of Orphan Medicinal Products (COMP) can be a particularly challenging task for sponsors. Here, we identify and examine three common issues with the estimation of prevalence in orphan drug applications in the EU (the discernment between diagnosed and undiagnosed cases; the duration of the disease; and the need for an explicit contemporary conclusion) as critical factors for acceptable prevalence estimation. These concerns are discussed in detail based on recent examples of applications, which are reflected in published European Medicines Agency (EMA) documents.

在欧洲联盟（EU）的孤儿药产品指定立法框架中，确定一种状况影响不到10,000人中的五分之一，这是基于稀有性进行申请的先决条件。向孤儿药品委员会（COMP）证明这一要求对于申办者而言可能是一项特别具有挑战性的任务。在这里，我们确定并检查了三个常见问题，将其作为欧盟可接受的关键因素，以估算欧盟孤儿药的使用率（已诊断病例与未诊断病例之间的区别；疾病的持续时间；需要明确的当代结论）。患病率估算。基于最近的应用示例对这些问题进行了详细讨论，这些示例在已发布的欧洲药品管理局（EMA）文件中得到了反映。