Human Factors (or Usability Engineering)

‍Human Factors are defined as the study of the interactions between humans and the device (i.e., interface) and the subsequent design of the device-human interface.

The concepts of Human Factors (HF) and Usability Engineering (UE) are critical, mandatory components of the Design Controls and risk management process for medical devices regulated by the FDA.

This field plays an important role in Design Control and is intended to support manufacturers in improving device design to minimize potential use errors and resulting harm. The ultimate goal is to maximize the likelihood that new medical devices will be safe and effective for the intended users, uses, and use environments.

Frequently Asked Questions (FAQs) Associated with Human Factors/Usability Engineering

1. Why are Human Factors and Usability Engineering mandatory for medical devices?

The FDA developed guidance documents specifically to assist industry in applying HF/UE processes to ensure new medical devices are safe and effective. These recommendations help manufacturers assess and reduce risks associated with medical device use.

HF is a key component of the Design Input requirements for a device.

2. When is Human Factors or Usability testing required?

Usability testing is frequently mandated as a special control for various classes of medical devices, particularly Class II devices, often referred to as Human Factors validation, Human Factors testing, or usability testing.

This requirement is integrated into the overall Design Validation phase, which ensures the device conforms to defined user needs and intended uses.

3. What must Human Factors testing typically demonstrate?

For many devices, HF or usability testing must demonstrate that the intended user can safely and correctly use the device for its intended use.

Specifically, usability testing often verifies that the user can correctly use the device:

• Based solely on reading the directions for use/labeling.
• Including the user’s ability to correctly interpret the device output and understand when to seek medical care.
• For devices requiring complex user interaction (like intervention planning software), the evaluation must assess the user interface and labeling to allow users to correctly use the device and interpret the provided information.

4. Are there specific types of usability studies mandated for consumer-facing devices?

Yes, for devices intended for use by a lay user or over-the-counter (OTC) use, the regulations define specific requirements for user studies:

• Genetic Health Risk (GHR) Assessment Devices (OTC): Must include a user comprehension study to demonstrate that the educational module and test reports are adequate for OTC use. This study must meet a predefined primary endpoint criterion, which typically requires a minimum of 90 percent or greater overall comprehension rate for each comprehension concept tested (e.g., purpose of test, results, limitations). Study participants must be untrained, naive to the test subject, and provided only the materials that will be available when the test is marketed.
• Aesthetic OTC Devices: Require label comprehension and self-selection performance evaluation to demonstrate that users can understand the package labeling and correctly choose the device.

5. How does Human Factors relate to Risk Mitigation (Training and Labeling)?

The findings from usability and human factors analysis are crucial inputs to risk mitigation strategies:

• Risk Mitigation through Training: As part of risk management activities performed under design controls (21 CFR 820.30), manufacturers must document an appropriate end user device training program to mitigate the risk of failure to correctly operate the instrument. Training programs themselves must sometimes be validated by human factors testing and analysis to ensure users can follow the instructions for safe use.
• Risk Mitigation through Labeling: Labeling is considered the final, and least effective, layer of control. HF testing ensures the labeling is sufficient for effective use, and labeling often includes warnings identifying sensor acquisition factors, user errors, or other factors that may impact measurement results. For many systems, testing must demonstrate the user can correctly use the device based solely on reading the instructions for use.

6. What other specific requirements involve Human Factors testing?

Human Factors studies are specified as necessary components in the review process for complex devices to evaluate the safety of the user interface:

• Interventional Imaging Systems: Require Human Factors evaluation to assess the ability of the user interface and labeling to allow users to correctly use the device and interpret provided information.
• Surgical Systems: Require Human Factors validation testing to demonstrate that the user interfaces of the system support safe use in an operating room environment.
• Gastrointestinal Devices: Require Human factors testing to demonstrate that intended users can safely and correctly use the device.
• Whole Slide Imaging Systems: A detailed human factor engineering process must be used to evaluate the system user interface(s).

‍