Use errors and abnormal use describe different reasons why a medical device is not used as intended. A use error occurs when the user’s action or omission leads to an outcome different from what was expected or intended by the manufacturer. Abnormal use, by contrast, occurs when the intended purpose is deliberately violated.
Use errors at the human–device interface
A use error may result from inattention, memory lapses, an operating mistake, or a lack of understanding of how to use the device. From a regulatory perspective, not every operating error is automatically an incident. The specific link to vigilance arises when the product’s ergonomic design caused the error. Ergonomic features are specifically intended to support the intended user in safe and effective use.
The investigation therefore does not only ask who pressed a button or skipped a step. It considers the display, alarm, connector design, labeling, instructions for use, training, and the use environment. If this shows that the interface facilitated the incorrect use, the error may be attributable to a product characteristic. Such a finding requires an assessment of the potential consequences for other users and may trigger changes to design, labeling, or risk controls.
Deliberate violation of the intended purpose
Abnormal use is an intentional act or omission that contradicts normal use and lies outside any further reasonable, interface-related risk controls by the manufacturer. The classification therefore hinges on the deliberate violation of the intended purpose, not solely on the undesired outcome. The established term “off-label use” is an obvious example: Use outside the instructions for use may be abnormal if it is deliberately chosen.
Even in cases of abnormal use, the case remains relevant for quality management. The manufacturer documents it and assesses whether the observed practice indicates unclear information, a previously unrecognized user group, or a systematic need. This does not make the deliberate rule violation a reportable, ergonomically caused use error. However, a documented decision trail helps prevent recurring signals from disappearing from complaints or field feedback without expert assessment.
Distinction from reasonably foreseeable misuse
Between the two terms lies reasonably foreseeable misuse from a risk management perspective. It includes ways of use that are not intended, but whose occurrence can be expected due to the product, the target group, or the use environment. Such scenarios belong in the risk analysis and can be addressed through design, protective measures, or information.
A use error is observed in a specific case; reasonably foreseeable misuse is initially a risk to be considered prospectively. Abnormal use, by contrast, denotes a deliberate boundary crossing that goes beyond appropriate interface controls. This three-way distinction prevents two incorrect decisions: the quality file must not dismiss an ergonomically contributed error as mere misconduct, and it must not treat every intentional misuse as a design failure.
The case description should reflect the observed use in chronological order. Informative details include, for example, the setting visible on the device, the message displayed, the accessory combination used, and the instructions previously received. A retrospective attribution such as “user error” is not sufficient, because it leaves open the key question of whether the product was designed to be understandable and error-tolerant for its reasonably foreseeable user group.
Relevance for clinical trials
In clinical investigations, training, instructions for use, inclusion and exclusion criteria, and the guidance at the investigational site become part of the evidence-relevant use situation. If an investigational result is distorted by an unclear operating sequence or a patient is exposed to an avoidable hazard, the team must capture the process in a way that allows design cause, training gap, and deliberate deviation to be distinguished. This affects both the safety assessment and the interpretability of the performance data collected.
Full-service CROs such as Mediconomics provide support through user-focused reporting forms, training materials for investigational sites, coding of device deficiencies, and alignment between clinical monitoring and risk management. They can also assess whether clustering at a site indicates a training issue, a particular version of the instructions for use, or a need for ergonomic changes.
For follow-up investigations, organizational culture must not distort the description. Neutral capture of the situation makes it easier to separate technical causes from training or behavioral aspects and to select the appropriate follow-up actions.
Frequently Asked Questions (FAQ)
When does a use error become an incident?
It is classified as an incident when it is attributable to ergonomic characteristics of the product. It must then also be assessed whether the criteria for a serious incident are met.
Is every off-label use abnormal use?
The guideline cites off-label use as a possible example. The decisive factors remain whether the user deliberately violates the intended purpose and whether the action lies outside any further reasonable interface risk controls.
Why must non-reportable cases also be documented?
They may reveal patterns related to training, labeling, or actual use. These insights feed into risk assessment and potential improvements to the product.
Regulatory References
- Regulation (EU) 2017/745, Article 2(64) – includes ergonomically caused use errors within the definition of an incident.
- Regulation (EU) 2017/746, Article 2(67) – contains the corresponding definition for in vitro diagnostic medical devices.
- MDCG 2023-3 Rev.2, Questions on use error and abnormal use – explains causes, documentation, and delineation.
- Regulation (EU) 2017/745, Annex I – requires consideration of risks arising from intended use.
