How to Reduce the Burden of Iterative Design and Evaluation

Learn about the analytical human factors techniques that help maximize the likelihood that a medical product will be safe and effective for the intended users, uses, and use environments.

Suresh P. Gupta

November 15, 2017

7 Min Read
How to Reduce the Burden of Iterative Design and Evaluation

Many professionals at pharmaceutical and medical device companies associate human factors engineering (HFE) with merely usability testing, meaning a formative or validation study. Although usability testing is an important aspect of the HFE process, it is only part of the picture. Moreover, usability testing is often carried out relatively late in the development process, where any required changes to the design as a result of testing can cost a lot of money, delay the process significantly, or in the worst case, kill development.

HFE is much broader than just conducting usability testing. It is an integral part of the medical product development process and includes both analytical activities that do not involve usability testing with users, and empirical activities such as user studies. This article describes the interconnectivity of the analytical activities with the overall HFE process and highlights the importance of these activities in terms of the overall goal of the HFE process from the regulatory perspective. It also describes three widely used techniques to conduct these analyses and demonstrates the value of these techniques through real-world examples. The techniques discussed in this article are applicable to a wide range of medical products, including combination products such as inhalers and injectors. Inhalers are used as an example here.


Figure 1 presents the regulatory HFE process and requirements in a simple schematic way, explaining the essential elements of the process. The process described in Figure 1 is based on FDA’s Guidance Documents and the International Standard IEC 62366-1:2015.

Figure 1—HFE regulatory process and requirements

The HFE process, as shown in Figure 1, is designed around the key focus of the regulatory requirements, namely the safety and effectiveness. It is essentially a risk-based approach linked with the risk management process.

Many manufacturers dive straight into the design of their product, but this can unfortunately lead to a vicious cycle of design iteration and evaluation via usability testing. If the design is too mature and the usability testing still identifies significant use errors, the manufacturers often have no option other than to rely entirely on their Instructions for Use (IFU) to mitigate the problems and, in the worst case, on providing training to the users. Unfortunately, some products are killed at this stage because even the most effective IFU or training program can only do so much to mitigate all significant risks.

Therefore, it is essential to identify and analyze potential use-related problems at the outset of the design process so that the design can be tailored to address these problems. There are various ways to do this. These can be termed Analytical HFE Activities, or what FDA calls Preliminary Analyses. The focus of these activities is to identify and analyze potential use-related problems with the device under development with the purpose of guiding the design of the product to avoid or mitigate such problems.

Many manufacturers conduct the Preliminary Analyses retrospectively, especially when they start to prepare their dossier for submission and realize that they have not done the Preliminary Analyses, which are required by the regulatory bodies. This defeats the purpose of the analyses, but more importantly, what if the analyses highlight significant use-related problems at this stage which, obviously, the usability testing had failed to identify? The human factors or usability studies are done with relatively small samples (5–8 for formative studies and 15–20 for validation studies) and there is no guarantee that these studies will always identify those problems. A successful validation study on its own is also not a guarantee that the product is safe and effective, unless complementary techniques such the Preliminary Analyses are done. Also, if these studies are not designed to include critical tasks—user tasks that could pose harm to users, identified through Preliminary Analyses—then they will not identify these problems.

Therefore, conducting the Preliminary Analyses is highly recommended. These analyses are done by means of analytical methods which are both cost effective and less time consuming. This article describes three key methods that will serve this purpose and also satisfy regulatory requirements.

Analytical HFE Activities (Preliminary Analyses)

There are many ways and methods by which potential use-related problems that affect the safety and effectiveness of a product can be identified and analyzed. At a bare minimum, three key methods, as shown in Figure 2, are suggested: Identification of Known Use Problems, Task Analysis, and Use-related Risk Assessment.

Figure 2—Methods for Preliminary Analyses

Identification of Known Use Problems

Regulatory bodies suggest that manufacturers should investigate use-related problems that have occurred in the past with devices that are similar to the one under development so that they can be addressed in the new design. Information regarding the use-related problems can be obtained through various means, such as by reviewing customer complaint files of similar products, reviewing published articles, and searching publicly available device incident databases, such as FDA’s Manufacturer and User Facility Device Experience (MAUDE) database. Database searches may identify a good range of use-related problems on a minimal budget and short timeline. Some of these databases contain a very large number of reports that can be searched and retrieved for free. For more information on a method for conducting these database searches, analyzing the data, and reporting the findings in a systematic way, refer to this peer-reviewed journal paper.

Task Analysis

Task analysis is a well-established but simple technique that includes systematically breaking down the device use process into a sequence of user tasks and sub tasks. This allows one to then analyze each task to identify the users involved at each task, the user interface component of the device, and the potential errors that users could make at each task.

Task analysis is conducted at various levels. At a minimum, a task analysis can simply be a decomposition of the device use process into a sequence of tasks. For example, a task analysis for a simple pressurized Metered Dose Inhaler (pMDI) would look like a list of user tasks, as presented in Table 1.

Table 1—A simple task analysis for a typical pressurized Metered Dose Inhaler (pMDI)

The task analysis can be extended further to identify potential use errors which become the basis for a use-related risk assessment, discussed in the following section. The task analysis can also be used for other purposes, such as to define the operating principle of the device or to develop the IFU.

Use-related Risk Assessment

There are a number of risk assessment methods that can be used to conduct a use-related risk assessment. One widely recognized method that is often used in the pharmaceutical and medical device industry is the Failure Modes and Effects Analysis (FMEA). With this method, a team of individuals with experience using the device, clinical experts, design engineers, and human factors specialists look at each user task—generated by a Task Analysis—and brainstorms possible use scenarios that could lead to a use error, and considers potential harm for each possible use error. The risk assessment file is updated periodically, such as after a formative study, to make sure all risks are considered and mitigated to an acceptable level. The final validation study findings, as shown in Figure 1, are also fed into the risk assessment to be able to demonstrate that the product is safe and effective, and conclude that any residual risks are outweighed by the benefits of the product.

Examples of Findings of Preliminary Analyses

The Preliminary Analyses methods described above were utilized to understand potential use problems with current inhaler devices on the market. A number of issues were identified throughout each step of the inhalers’ use process. Table 2 presents a generic inhaler use process and highlights some of the issues identified. While this is not exhaustive coverage of potential use problems, it highlights the importance and usefulness of the Preliminary Analyses in identifying these problems.

Table 2—Potential use-related problems with inhaler use

Although not all potential use-related problems have been presented in this article, it is evident from Table 2 that the Preliminary Analyses are a powerful approach to identifying problems at the outset of the design process without having to conduct costly usability testing such as a user study. However, the Preliminary Analyses do not replace the usability testing. They are complementary HFE activities.


HFE is an integral part of the medical product development process, helping manufacturers develop safe, effective, and usable products. It has a much broader remit than just conducting usability testing such as a formative or validation study. It utilizes a number of complementary activities and techniques including Preliminary Analyses which has been the focus of this article. Preliminary Analyses—Identification of Known Use Problems, Task Analysis, and Use-related Risk Assessment—should be conducted at the outset of the design and development process of a medical product in order to identify use-related problems so that they can be addressed through design. These analyses will not only satisfy the regulatory requirements but also reduce the burden of the iterative design and evaluation cycle further down the development process, and maximize the likelihood that the medical product will be safe and effective for the intended users, uses, and use environments.

About the Author(s)

Suresh P. Gupta

Suresh P. Gupta, PhD, is head of Human Factors and Usability Engineering at Cambridge Consultants in Cambridge, UK. 

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