All terms
Adverse Event
Any untoward medical occurrence in a subject, whether or not related to the device.
Reviewed by Christian Espinosa, Founder, Blue Goat CyberLast reviewed May 5, 2026
Definition
Per ISO 14155, an adverse event is any untoward medical occurrence, unintended disease or injury, or untoward clinical signs in subjects, users, or other persons, whether or not related to the investigational device. What the regulation says
Regulators like the FDA and those operating under the EU MDR mandate the reporting of adverse events to ensure patient safety and device effectiveness. The FDA’s 21 CFR Part 803 outlines medical device reporting requirements, while the EU MDR (Regulation (EU) 2017/745) details vigilance and post-market surveillance obligations, including the reporting of serious incidents. ISO 14155, specifically clause 7, provides guidance on recording and reporting adverse events in clinical investigations.What this means in practice
AEs are the foundational unit of clinical safety reporting. Serious AEs (SAEs) and device-related AEs (ADEs/SADEs) trigger expedited reporting obligations.Examples
- A patient implanted with a cardiac pacemaker experiences an unexpected infection at the implant site, which is identified as an adverse event.
- During a clinical trial for a new glucose monitor, a participant reports a localized skin rash at the sensor application site, constituting an adverse event.
- A user of an insulin pump experiences a hypoglycemic episode that requires emergency medical intervention, categorized as a serious adverse event.
Common pitfalls
- •Confusing an adverse event with a device malfunction that did not lead to an adverse clinical outcome, as these have distinct reporting pathways.
- •Failing to initiate an investigation or report an adverse event due to a perceived lack of direct causal link to the device, as all untoward occurrences must be assessed.
- •Delaying the reporting of serious adverse events (SAEs) beyond the mandated regulatory timelines, which can lead to non-compliance.
- •Not adequately documenting the assessment of causality between the device and the adverse event, which is critical for regulatory review.
- •Inconsistently applying definitions of "serious" across different studies or reporting jurisdictions, causing reporting errors.
Frequently asked questions
An adverse event is any untoward medical occurrence, while a serious adverse event meets specific criteria, such as leading to death, a serious deterioration in health, or requiring hospitalization, as defined by regulations like the EU MDR Annex XVI and FDA 21 CFR 803.3.
Cross-references
Related terms
Shared paths + categoryStandards
ISO 14155
Good clinical practice for clinical investigations of medical devices.
Clinical Trials & Evidence
Post-Market
Medical Device Reporting (FDA)(MDR)
FDA mechanism for receiving reports of device-related deaths, serious injuries, and malfunctions.
Post-Market
Medical Device Vigilance
Reporting and management of serious incidents and field safety corrective actions.
Clinical & Trials
Feasibility Study
Small clinical study evaluating initial safety, usability, and design parameters of an investigational device.
Clinical Trials & Evidence · adjacent
Clinical & Trials
Surrogate Endpoint
Biomarker or intermediate outcome used as a substitute for a clinical endpoint in regulatory decisions.
Clinical Trials & Evidence · adjacent
Clinical & Trials
Adaptive Trial Design
Trial design that pre-specifies opportunities to modify aspects (sample size, arms, endpoints) based on interim data.
Clinical Trials & Evidence
Latest in MedTech
Primary references
3 sourcesLink health: 3 verified· last checked 2026-06-20
ISO·1FDA·1NIH·1
- 1ISO 14155 AE definitionsVerifiedISOiso.org
- 2FDA - Clinical Trials and Human Subject ProtectionVerifiedFDAfda.gov
- 3ClinicalTrials.govVerifiedNIHclinicaltrials.gov
Inline markers like [1] jump to the matching reference above.