August 4, 2020
Use-related risk analysis (URRA) is a cornerstone activity for a thorough human factors engineering (HFE) process that meets the expectations set forth by US FDA and international reviewers. A complete and well-considered URRA, such as a Use Failure Modes and Effects Analysis (uFMEA), helps to make sure that use-related risks are considered and mitigated to an acceptable level throughout the development process. Further, URRA serves as the basis for the scope of tasks evaluated in an HF validation test, the culminative HFE activity that seeks to evaluate whether a product can be used safely and effectively.
What steps should you take to develop a URRA? Below, we outline 10 steps to conducting an effective URRA. We use a medication delivery device as an example throughout. However, these steps can readily be adapted to developing a URRA for more complex medical technology as well.
- Conduct task analysis. First, conduct a detailed task analysis, breaking down the use of the product into specific, discrete steps. Consider all of the touchpoints of the device, and how the user will interact with them. During this analysis, focus on the user’s interaction with the device and consider how the user could make errors of perception, cognition, and action. For example:
- Error of perception: User does not realize the device is out of medication.
- Error of cognition: User thinks they have delivered a dose of medication but they have not.
- Error of action: User delivers twice the appropriate dose.
(The task analysis will result in a list of tasks. Tasks are individual actions the user will complete when interacting with the device. For example, tasks could include cleaning the injection site, inserting the needle into the skin, or discarding the needle after injecting.)
- Conduct hazard analysis. Next, conduct a hazard analysis. A hazard is the thing (e.g., physical item, chemical reaction) that causes a user harm. A simple way to think about hazards is using the example of falling – when one falls, the floor is the hazard. During the hazard analysis, identify all of the hazards associated with your device. Much of this analysis might focus on underdosing or overdosing for a medication delivery device.
- Next, identify a hazard for each task. Notably, there could be more than one hazard for each use scenario/task.
- Identify use errors. Next, identify a use error for each task/hazard (we’ll call this collection a “risk line item” because it is associated with one row in a URRA table). A use error is the action the user takes that does not meet the manufacturer’s expectations. Examples of use errors could include the user withdrawing the incorrect volume of medication into the device, injecting into the incorrect location, or injecting at the incorrect angle. Notably, you might identify several use errors for each task.
- Identify hazardous situations. For each line item, identify a hazardous situation. Think of the hazardous situation as the link between the use error and the harm – it explains how the error could cause the user (or someone else) harm. For example, if a user withdrew the wrong volume of medication into the device (use error), the device would deliver the incorrect dose to the patient (hazardous situation), leading to harm. Notably, you might identify several hazardous situations for each use error.
- Identify harm. Next, identify the associated harm. The harm is what could occur to the user (or someone else) if the use error and hazardous situation occur. Following the example in the Bullet Four, the harm could be a temporary (short-term) persistence of the patient’s condition.
- Rate severity and probability. For each risk line item resulting from the above steps, identify the risk’s severity and probability. Most manufacturers have a quality system process explaining their approach to this rating.
- Identify risk rating. To identify the risk rating for each risk line item, multiply the severity and probability (Bullet Six) together. Many manufacturers have a quality system process explaining their approach to this rating (i.e., it is often used to identify which risks must be mitigated).
- Identify whether each risk line item is critical or non-critical. In general, you will identify a severity “threshold.” Any risk line item with a severity above that threshold will be considered “critical,” and any risk with a rating below that threshold will be considered non-critical. The items determined to be critical tasks serve as the basis for the use scenarios evaluated in the HF validation test.
- List mitigations. For each risk, identify the mitigations that are in place to either (1) reduce the likelihood that a user encounters the risk, or (2) reduce the risk’s severity. Identifying mitigations is an excellent opportunity to support your assertion to regulators that your device is safe for use. Conversely, this activity might be an opportunity to identify which necessary mitigations are not currently in place in the device design.
- Identify severity, probability, and risk rating post-mitigation. Consider your device within the context of the mitigations you have in place, and re-rate the severity and probability to generate post-mitigation risk as described above.
Upon performing these 10 steps, you will have completed an important component of your HFE process. Bear in mind that the URRA should be treated as a living document, so make sure to update it regularly throughout your development process.
Andrea Dwyer is Associate Research Director and Alexandria Trombley is Senior Human Factors Specialist at Emergo by UL’s Human Factors Research & Design (HFR&D) unit.