How to Plan and Run Formative Usability Studies for Medical Devices

Formative usability studies is an important stage of medical device development, where many of the most important design decisions are either confirmed or challenged. They sit upstream of validation, at a point where change is still possible and learning still has significant value. When approached properly, they shape safer devices and more robust regulatory outcomes.

Despite this, formative usability testing is often misunderstood.

It is sometimes treated as a scaled-down rehearsal for summative testing, or as a regulatory obligation to be addressed later. In reality, formative studies are a design tool. They exist to inform decisions while there is still room to act on what is discovered.

Planning and running these studies well requires intent and structure, alongside an understanding of how usability evidence fits within the broader medical device design process. Let’s dive into their importance.

Why Formative Studies Exist

Formative usability testing is defined within IEC 62366 as a means of evaluating user interaction with a device during development. The purpose is not to prove compliance. It is to uncover use-related risks and friction points that can be addressed through design.

In practice, this means formative studies should happen early enough to influence aspects like architecture, interaction design and task flow. If a study only confirms that a finished interface works, its value has already been limited. The most useful insights tend to surface when concepts are still flexible and assumptions can still be questioned.

This distinction is important. Formative testing informs design intent. Summative testing confirms that intent has been realised.

Defining the Right Scope

A common mistake in formative usability work is trying to test too much at once. Early studies are most effective when they focus on specific tasks or interactions rather than attempting to assess the entire system in one session.

At IDC, we define scope by looking at where uncertainty sits within the design. This might be a critical user task, a new interaction model or a scenario where misuse could have significant consequences. By narrowing focus, studies become more revealing and less performative.

Scope should also reflect the maturity of the design. Early formative studies may use low-fidelity prototypes or simulated interactions. Later studies can become more representative as design intent stabilises. What matters is that the level of fidelity supports learning rather than creating false confidence.

Recruiting the Right Participants

This is a vital factor - participants must reflect the intended user population as closely as possible, including factors like:

• Experience level

• Physical capability

• Likely context of use

For medical devices, this often means recruiting a mix of primary users and secondary users where appropriate. In home use scenarios, carers or family members may interact with the device in ways that differ from clinical staff. Ignoring these differences can leave critical gaps in understanding.

Recruitment criteria should be clearly defined and documented. This supports both the quality of the study and its regulatory credibility later. It also ensures that findings can be interpreted with confidence rather than explained away.

Designing Test Protocols That Reveal Reality

A good formative test protocol encourages natural behaviour. Participants should be asked to complete realistic tasks using the information and cues they would have access to in real use. Over-instruction risks masking usability issues rather than revealing them.

We design protocols which focus on what users do, not what they say they would do. Observation is often more valuable than questioning, particularly when users are navigating unfamiliar interfaces. Hesitation and errors provide insight that direct feedback may not capture.

The goal is not to lead participants to success, but to understand where design supports or obstructs safe use. That mindset shapes how tasks are introduced and how facilitators interact during sessions.

Capturing and Interpreting Data

Formative usability studies generate qualitative data that must be handled carefully. Recordings and observations should be structured so that patterns can be identified across participants without losing context.

At this stage, analysis is all about understanding why certain behaviours occur. When users struggle, the question is not whether they are capable, but what the design is asking of them. This perspective keeps responsibility where it belongs.

Findings should be traceable back to specific design elements and tasks. This makes it easier to translate insights into design changes and to demonstrate how usability considerations have informed development over time.

Using Findings to Drive Design Decisions

The value of formative testing lies in what happens next. Insights should lead directly to design action, whether that involves changing interaction flow or revisiting assumptions made earlier in development.

This is where formative usability testing becomes embedded in the medical device design process rather than existing alongside it. Design iterations are informed by evidence, and each study builds on the last. Over time, uncertainty reduces and confidence increases.

This iterative relationship between design and usability is central to how we approach human factors within our broader medical work.

Maintaining Alignment with IEC 62366

While formative studies are exploratory by nature, they must still align with regulatory expectations. Documentation should clearly state the purpose of each study, as well as the rationale for participant selection and how findings have influenced design.

This alignment requires high levels of clarity. When formative usability work is planned deliberately and integrated into development, regulatory traceability becomes a natural by-product rather than an administrative burden.

By the time summative testing is approached, the device should already reflect a series of informed usability decisions rather than last-minute adjustments.

Formative Testing as a Design Discipline

When treated as an established way of working, formative usability becomes one of the most effective tools for reducing risk and improving user experience in medical device development.

Well-planned studies surface issues early, while guiding design direction and supporting safer outcomes for users. They also create a stronger foundation for regulatory approval by demonstrating that usability has been considered throughout development.

That is why formative usability testing remains a central part of how we design medical devices, from early concepts through to validated solutions.