As UX researchers specializing in medical devices, we often receive questions from manufacturers outside Japan who are looking to enter the Japanese market. One of the most common is:
“How should we recruit participants for a usability evaluation in Japan?”
While you might be familiar with established practices for usability testing in the U.S. and Europe, recruiting for a usability evaluation intended for a PMDA submission in Japan has its own unique considerations.
In this article, we explain how participant recruitment works for usability evaluations conducted for PMDA submissions.
A quick note: For any medical device submission in Japan, compliance with JIS T 62366-1:2022 (Application of usability engineering to medical devices) is mandatory.
(For a deeper dive into the fundamentals of usability evaluation, you can also read our previous article here. )
Common Questions About Usability Evaluation in Japan
If you’re planning a medical device usability study in Japan, you probably have questions like these:
- “How do you actually recruit participants in Japan?”
- “What kind of users should we be targeting?”
- “What’s the required sample size?”
In usability engineering, the “context of use”—which includes the user, the use environment, and the use scenario—is paramount. You need to understand how the user and the medical device will interact in a specific environment and reflect those conditions in your evaluation.
This means that who you recruit as participants directly impacts the quality and validity of your entire evaluation.
Recruiting the Right Participants for Your Study
The approach to recruitment for medical device usability evaluations depends on the goal of the study. There are two main phases of evaluation, each requiring a different type of participant: Formative Evaluation and Summative Evaluation.
Formative Evaluation:
This is primarily conducted to improve the design during the development process. The main goal is to identify usability issues early on. At this stage, it’s possible to proceed with participants who may not be a perfect match for the actual end-users.
Summative Evaluation:
This is the final validation to verify the safety of the finished product and is a critical part of your submission dossier to the PMDA. For this, it is essential to recruit participants who are “truly representative of the intended users.” This concept of “representativeness” is the key to a successful submission. In regulatory documentation, these studies are often referred to as PMDA usability testing or human factors validation studies.
For example, the ideal participant profile changes depending on the device’s intended user:
- A device for a rare disease → Patients diagnosed with that specific disease.
- A device operated by healthcare professionals (HCPs) → Physicians, nurses, or other relevant HCPs.
- A home-use medical device → The patient themselves, or their family members and caregivers.
With the rise of SaMD (Software as a Medical Device) and AI-powered devices, the user landscape is becoming even more diverse. Your target users might not just be doctors and nurses, but also patients, their families, and informal caregivers.
Four Practical Considerations When Planning Recruitment
To build a compelling submission for the PMDA, you need to strategically consider the following four points. Let’s break each one down, following the typical thought process for planning a project in Japan.
- Representativeness: Who are the “right” users?
- Sample Size: How many participants do you need?
- Methods: How do you find them?
- Difficulty: How long will it take, and what are the challenges?
Below, we look at each of these in more detail.
1. Representativeness: Defining a High-Resolution User Profile
What does it really mean to be “representative of the user”? To create objective evidence that will be convincing to the PMDA, you must carefully define your participant profiles by considering a variety of attributes:
- User Groups: Are they physicians, nurses, clinical engineers, patients, or family members?
- Expertise and Proficiency: What is their level of knowledge and experience with the device or procedure (e.g., novice vs. experienced, specialist vs. general practitioner)?
- Physical and Cognitive Characteristics: What are their age, gender, physical limitations, or specific health conditions?
- Cultural Context: What is their familiarity with Japanese medical practices and general IT literacy?
- Use Environment: Will the device be used in an operating room in a large hospital, a consultation room in a small clinic, or a home setting?
For instance, an evaluation for a new surgical robot might require “surgeons with over 10 years of laparoscopic surgery experience,” while a study for a new self-injection device might target “a 70-year-old rheumatoid arthritis patient using a self-injector for the first time.”
2. Sample Size: The “Rational Justification” Required by the PMDA
“How many people do we need to recruit?” This is another question I hear all the time.
Interestingly, unlike the FDA, which often suggests a minimum of 15 participants per user group*, Japan’s PMDA does not specify a concrete number. Instead, the PMDA places significant emphasis on the rationale explaining why your chosen sample size is sufficient.
This doesn’t mean you can get away with a small sample. On the contrary, the burden is on you, the manufacturer, to logically justify why your sample size is adequate to represent the user population and validate the device’s safety.
A larger sample size and a more robust justification are typically expected in cases such as:
- High-risk devices (Class III or IV)
- Software as a Medical Device (SaMD), especially those incorporating AI
- Devices intended for use by laypeople (non-professionals) in home settings
* The guidance document (IEC TR 62366-2) suggests a general benchmark of “at least 15 participants per user group.”
(We cover sample size and evaluation environments in more detail in this article.)
3. Recruitment Methods in Japan
So, how do you find participants in Japan who match your defined user profiles? At Uism, we strategically combine several methods:
- Specialized Medical Recruiting Agencies: These firms maintain panels (lists of registered individuals) of HCPs and patients with specific conditions. This can be a quick way to screen candidates, but they may not be able to find participants for highly specific criteria.
- Patient Advocacy Groups and Family Associations: These are communities for patients with specific diseases and their families. Approaching them requires building trust and proceeding with care, but it can lead to incredibly high-quality and motivated participants.
- Collaboration with Patient-Focused Service Companies: A newer method involves partnering with companies that run online communities or patient-support apps for specific disease areas.
- Our Professional Network: In addition to the above, we leverage the personal connections with HCPs that we’ve built over years of research. This often becomes an effective way to identify highly specialized experts who are not accessible through public channels.
(For a detailed breakdown of the pros and cons of each recruitment method, see this article.)
4. User Groups and Recruitment Difficulty
Just because these methods exist doesn’t mean finding participants is easy. In Japan, each user group presents its own set of challenges. Here is a guide to the typical difficulty and timeline based on our experience, which should be helpful for your project planning.
| User Group | Difficulty* | Recruitment Hurdles and Solutions |
| Doctors | ★★★☆☆ | Tight Schedules and Institutional Requirements Doctors in Japan are incredibly busy, juggling outpatient clinics, inpatient rounds, surgeries, research, and academic conferences. Scheduling even a few hours for a study can be a major challenge. How to Overcome: ● Understand institutional differences: Doctors at university hospitals often face complex internal procedures, while private clinic owners may have more flexibility outside of their consultation hours. ● Anticipate internal approval processes: Especially at large hospitals, participation may require formal internal approval, including permission from a department head (e.g., a professor). Payment rules can also be strict; some institutions prohibit direct personal payments. ● Recognize that KOLs are different: Key Opinion Leaders (KOLs) are in a league of their own. Standard recruitment methods will not work. Accessing them requires a strong, pre-existing relationship and a robust professional network. |
| Nurses & Other HCPs | ★★★★☆ | Unpredictable Shift Work and Consideration for Fatigue Most nurses and other paramedical staff work irregular shifts (day, evening, night). Their schedules are often not confirmed even a month in advance, making scheduling arguably even more challenging than with doctors. How to Overcome: ● Be extremely flexible: Offer multiple scheduling options, including evenings and weekends, and be prepared to accommodate their availability. ● Design the study with fatigue in mind: It’s not uncommon for participants to arrive “post-night-shift.” To ensure data quality, consider their potential lack of focus. This may mean shortening the session or avoiding overly complex tasks. |
| General Patients | ★★★☆☆ | Work-Life Balance and the Cultural Need to Consult Their Doctor Working-age patients often find it difficult to take time off on a weekday due to Japanese work culture. While older patients may have more flexible schedules, they can face challenges traveling to a facility or have fluctuating health conditions. How to Overcome: ● Accommodate diverse lifestyles: Offer evening/weekend sessions for working individuals, or consider online or in-home visits for elderly participants to lower the barrier to entry. ● Incorporate “doctor consultation” into your process: Patients in Japan have a strong cultural tendency to “first consult with my doctor” before agreeing to participate. Understanding this is key. Providing materials to help them explain the study to their physician can build trust and make them feel more comfortable. |
| Patients with Rare Diseases | ★★★★★ | Small Population Size and the Need for Ethical Sensitivity This is typically the most difficult group to recruit. For some diseases, the entire patient population in Japan may only be a few hundred people. Patient advocacy groups are often the only point of contact, but these are typically very closed communities that are difficult for outsiders to approach. How to Overcome: ● Trust is everything: Building long-term relationships with patient groups, support organizations, and specialist physicians is non-negotiable. If your project is perceived as purely commercial, the door will close instantly. ● The highest ethical standards are a prerequisite: Protecting participant privacy, being mindful of their physical and mental burden, and managing personal data with the strictest of care are more critical for this group than any other. This is a non-negotiable foundation for the project. |
| Family / Caregivers | ★★★★☆ | Feelings of “Not Being the Patient” and Their Double Burden Family and caregivers are valuable participants who offer a different perspective from the patient, but they come with unique recruitment challenges. Many feel a psychological hesitation: “I’m not the actual patient, so is it okay for me to give my opinion?” How to Overcome: ● Clearly explain their value: You must sincerely and specifically communicate why their perspective is so important, how their feedback will improve the product, and how that ultimately benefits the patient they care for. ● Acknowledge the caregiver’s own burden: Caregivers are under constant time and emotional pressure. Acknowledging their situation and expressing genuine gratitude—beyond just the monetary incentive—is crucial for building a positive relationship. |
*The difficulty levels and timelines are estimates. They can vary significantly depending on the specific recruitment criteria and the timing of the study.
*For medical studies, we typically recruit more backup participants (buffers) than for general usability studies, as last-minute cancellations due to health issues or denied permissions are more common.
Conclusion: The Key to Success is a Partner who Deeply Understands Japan’s Healthcare Landscape
In this article, we’ve covered the importance and the practicalities of participant recruitment for usability evaluations in the context of a PMDA medical device submission.
The PMDA doesn’t provide a simple checklist like “recruit X participants per user group.” Instead, it demands a rational justification for every decision you make: “Why are these participants representative of the intended users?” and “Why is this sample size sufficient to validate safety?”
To construct this “rational justification,” you need a recruitment strategy built on a deep understanding of Japanese clinical practices, the roles of different medical professions, and even the cultural context of patients.
Not confident in finding the right participants?
Timeline and recruitment process more complex than anticipated?
If you’re still unsure about the process or looking for someone to support you every step of the PMDA way, we’re here to help.
Uism has senior UX researchers with expertise in the medical device field. With a strong understanding of both global regulatory requirements and the local nuances of the Japanese market, we provide seamless end-to-end support, from strategic recruitment design to execution.
The regulations and necessities surrounding a PMDA submission may seem daunting at first, but we at Uism are dedicated to helping you bring your innovative medical devices to patients and healthcare professionals all across Japan. We look forward to putting our expertise to work for you.
References
- JIS T 62366-1:2022 (Medical devices – Part 1: Application of usability engineering to medical devices)
