Use Error

It is not necessarily a single physical document but can consist of several interlinked documents, provided the required contents can be found unambiguously and traced.

Purpose and function within the development process

The usability engineering file is the central proof of conformity for the application of usability engineering. It documents not only activities carried out but ensures the traceability of regulatory decisions. Auditors, notified bodies (the EU conformity assessment bodies) and authorities use the file to check whether use-related risks have been addressed appropriately. Particularly important is traceability between identified hazards, use requirements, development decisions, risk control measures and evaluation evidence.

Typical contents of the usability engineering file

The file typically contains the results of all essential steps of the usability engineering process:

• Documented planning of the usability engineering process
• Use specification
• Safety-related characteristics of the user interface and potential use errors
• Known or foreseeable hazards and hazardous situations
• Hazard-related use scenarios
• Selection of the hazard-related use scenarios for the summative evaluation
• User interface specification
• User interface evaluation plan
• Results of formative evaluations
• Results and analysis of the summative evaluation
• Justifications for improvements that were required or not carried out further
• Data for the assessment of the use-related residual risk
• References to related documents in the risk management or product development file

In many companies, individual documents lie outside the UEF, for example in the risk management file or in design input documents. The UEF then contains corresponding references.

Interplay with risk management

A common misconception is that the usability engineering file can be maintained independently of the risk management file. In fact, the modern usability engineering approach requires a close coupling between IEC 62366-1 and ISO 14971. Use errors, use difficulties and foreseeable misuse are identified in usability engineering and feed into the risk analysis. Conversely, risk-relevant user interactions from risk management must be taken into account in the usability engineering process. In audits, inconsistencies between the UEF and the risk management file are regularly found to be a weakness.

Evidence of development decisions

The usability engineering file should contain not only test results but also document the decision logic, for example why certain user interface concepts were chosen, which risks led to design changes, which insights were gained from formative investigations and why certain residual errors were accepted. Especially for complex medical devices, this traceability is often more important than the mere collection of individual artifacts.

Significance of formative and summative evaluations

Formative evaluations serve the iterative optimization of the user interface. Their results must be documented comprehensibly, including identified use problems and measures derived from them. The summative evaluation provides objective evidence, for the selected hazard-related use scenarios, that the user interface can be used safely under the specified conditions of use. A common shortcoming is that formative findings are not translated traceably into design changes or not traced back to the summative evaluation.

Common weaknesses in audits and reviews

Typical objections concern the missing link between use errors and risk management, incomplete documentation of critical tasks, missing justification for user groups or use scenarios, insufficient documentation of formative evaluations, missing traceability of design changes and unclear allocation of documents between the design history file, technical documentation and the UEF. Gaps frequently arise especially with legacy products when the file is reconstructed only retrospectively.

Regulatory reference

IEC 62366-1 requires the establishment and maintenance of a usability engineering file that documents the results of the usability engineering process or refers to corresponding documents. According to ISO 14971, use-related hazards and risk control measures are to be coordinated with the risk management process; in practice, this is usually implemented by linking the UEF and the risk management file. The EU MDR requires that ergonomic features, the intended users and the reduction of use-related risks be taken into account. In practice, the evidence is regularly provided through the usability engineering file. The FDA expects comprehensible human factors and usability evidence across the entire product lifecycle; the human factors documentation submitted for this corresponds functionally to a large extent to the contents of a UEF.

Frequently asked questions (FAQ)

Sources

• IEC 62366-1:2015+AMD1:2020, Medical devices, Part 1: Application of usability engineering to medical devices
• ISO 14971:2019, Medical devices, Application of risk management to medical devices
• Regulation (EU) 2017/745 on medical devices (MDR)

Related terms

• Risk management (ISO 14971)
• Formative usability evaluation
• Summative usability evaluation
• Use specification

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