Use Error

Central role in the usability engineering process

The intended use is one of the most important inputs for the use specification according to IEC 62366-1. The use specification makes the intended use more concrete, among other things through information on the medical indication, patient population, user profiles, use environments, and operating principle. Changes to the intended use therefore have a direct effect on human factors activities. An imprecise wording often leads to vague use scenarios and incomplete use-related risk analyses.

Delimitation from the use specification

The intended use answers the question of what a product is meant to be used for. The use specification, by contrast, describes in detail who uses the product, how, where, and under what conditions. In projects, the two concepts are often mixed up. An intended use alone is not sufficient to plan formative or summative usability tests, because additional information on users, tasks, and contexts is required for that.

Delimitation from indication for use

Especially in international projects, intended purpose and indication for use (the term used by the FDA) are confused. The intended use describes the intended medical benefit or function of the product. The indication, by contrast, describes the clinical condition, the disease, or the patient group for which the product is meant to be used. Both pieces of information are relevant for human factors activities, because they influence critical use scenarios and risk situations.

Influence on the use-related risk analysis

The use-related risk analysis according to IEC 62366-1 and ISO 14971 is based on the intended use of the product. The intended use defines the framework within which use errors are considered. Without a clear intended use, foreseeable sequences of events, hazardous situations, and critical tasks can be determined only incompletely. A common mistake is to assess uses that are not intended and the intended use together without a clear distinction. However, uses outside the intended use must not be excluded from the risk analysis across the board. Instead, it must be examined whether they are to be classified as reasonably foreseeable misuse, use error, or abnormal use.

Effects on formative and summative evaluations

Formative evaluations are used during design and implementation to examine the user interface, to identify use difficulties and need for improvement, and to assess the adequacy of design solutions. According to IEC 62366-1, the summative evaluation is meant to provide objective evidence that the user interface can be used safely with regard to the selected hazard-related use scenarios. It does not, however, replace clinical evidence that the product fulfills its full medical intended purpose. That is the subject of the clinical evaluation. If the intended use is extended or changed during development, the scope of the evaluation, the selection of participants, and the test tasks often have to be adapted.

Typical weaknesses in practice

Frequent problems are overly broad intended uses ("for all clinical environments"), missing information on user groups, or contradictory statements between the instructions for use, marketing materials, and technical documentation. Such inconsistencies regularly lead to findings in audits and by notified bodies (independent conformity assessment organizations designated by EU member states). From a human factors perspective, they make it particularly difficult to derive valid use scenarios and to justify the selection of participants for validation studies.

Delimitation from normal use (IEC 62366-1)

In German usage, "Zweckbestimmung" and "bestimmungsgemäße Verwendung" are mostly used synonymously. Under IEC 62366-1, however, a more precise distinction is worthwhile: The intended use (in MDR terms, the intended purpose) defines the medical purpose for which a product is intended. The additionally used term normal use denotes operation according to the instructions for use or, for products without instructions for use, according to generally accepted practice, including routine checks and adjustments by any user. Normal use covers both correct use and use errors and includes peripheral activities such as transport, storage, maintenance, and cleaning that go beyond the narrower medical purpose. Anyone who documents only the intended use in the narrow sense may not fully cover such peripheral activities. They belong in the use specification and must be added to the use-related risk analysis.

Regulatory reference

The MDR defines the intended purpose in Article 2 (point 12) as the use for which a device is intended according to the data supplied by the manufacturer. This includes the label, the instructions for use, promotional or sales materials, and statements, as well as information in the clinical evaluation. According to Annex II, the intended purpose is part of the general device description within the technical documentation. According to IEC 62366-1, the use specification is created on the basis of the intended use of the medical device. The intended use is thus an essential input for the usability engineering process. According to ISO 14971, risks must be considered and evaluated in the context of the intended use of the medical device; intended use and risk management are therefore directly linked. In the human factors process, the FDA requires or recommends the systematic consideration of the intended users, uses, use environments, and the user interface. Critical tasks are not simply defined here but are identified on the basis of the use-related risk analysis and form an essential basis for planning human factors validation.

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

• Use specification
• Use-related risk analysis (URRA)
• Validation
• Use requirements
• Intended user

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