Malfunction or deterioration in the characteristics or performance of a device

This phrase is part of the EU definition of an incident, so it decides whether an event enters vigilance assessment. MDCG 2023-3 links it to performance as the manufacturer states it, which means the claims in the technical documentation and labeling set the bar.

A ‘malfunction or deterioration in the characteristics or performance of a device’ can be described as a situation where a device fails to achieve, or is unable to uphold, the performance (Article 2(22) MDR) stated by the manufacturer when used in accordance with the information supplied with the device. For IVDs, the performance of a device (Article 2(39) IVDR) consists of the analytical and, where applicable, the clinical performance supporting its intended purpose. This device performance must be substantiated by the manufacturer in the technical documentation.

MDCG 2023-3 Rev.2, Question 3