Human Factors Submission Overview

Across numerous industries, it’s well known that every combination product or medical device submitted to the US Food and Drug Administration (FDA) requires a human factors assessment. These factors cover almost all aspects of a combination product or a medical device, ensuring that your design, labeling, instructions, and packaging promote your product’s safe use. 

In the context of regulatory submissions, human factors play a critical role in demonstrating that a product meets the necessary safety and performance requirements for its intended use. This article will provide an overview of the human factors (HF) regulatory submission process for medical devices and combination products. 

We’ll also cover different types of regulatory submissions that may be required, the key factors that must be considered when preparing a regulatory submission, and the importance of human factors in the regulatory review process.

What Are Human Factors?

Human Factors Engineering (HFE) is a scientific discipline focusing on understanding and designing the interaction between people using the medical device and the device’s user interface (UI). HFE is a key aspect of the product development process, as it ensures that the products are safe, effective, and easy to use by the intended user. 

The primary goal of HFE is to optimize the user interface, including all the UI components the end-user interacts with, to prepare the device for its intended use, use the device as intended by the manufacturer, or perform the necessary maintenance of the said device. 

Effective HFE optimization is achieved by minimizing use-related hazards and possible risks and subsequently confirming that the optimization efforts were successful through validation testing. There are several human factors research methods, including human factor studies, which are categorized as follows: 

  • Early Formative Studies — Early formative studies usually use five- or eight-user groups focusing purely on respective aspects of the UI rather than the entire UI. The goal is to evaluate product design, design alternatives, and user preferences and characteristics that would further influence design assumptions, device design, and design selection. 
  • Late-stage Formative Studies — These studies are used to assess more UI components together at one time, testing the entire UI in the process and emulating commercial design and validation research methodologies. Late-stage formatives are used to choose the device’s final design, its packaging, and the accompanying instructions, all of which increase readiness for a successful human factors validation. 
  • Summative or Validation Studies — Summative studies use larger sample groups compared to early formative studies, as they assess the entire UI and the final commercial design of the product. The goal is to demonstrate the use-related safety of the said product or its UI when used by the end user. 

It’s imperative to understand that HF studies are not marketing research, though the FDA recommends that HF information be documented in the medical device marketing submissions. Ideally, any human factors testing should precede any major preference or clinical studies. 

Human Factors Submission Framework

The submission framework is used to determine the category for human factors submission and the crucial information included in a marketing submission. According to the proposed FDA Guidance document, which complements the Usability Engineering to Medical Devices, including the HF information in the marketing submission can increase the FDA review efficiency by minimizing the number of requests for further data. 

The FDA draft guidance includes a flowchart that helps manufacturers choose the appropriate submission category; it’s based on the use-related risk analysis and indications for use. It also denotes whether the submission is for a brand-new product or a product that’s currently on the market. 

For example, an HF Submission Category 1 applies to a change to an existing device that doesn’t affect the UI, the device’s intended use, the intended use environment, use instructions, or labeling. However, this doesn’t apply to devices with a redesigned user interface. 

Devices with a redesigned UI, whose critical tasks weren’t affected in any way, and new devices with no critical tasks, would fall under HF Submission Category 2. Human Factors Submission Category 3 applies to new devices with critical tasks and pre-existing devices with newly added critical tasks or critical tasks that were affected by the UI redesign. 

What to Include

The FDA Human Factors Guidance document provides a detailed description of the types of human factors information that should be included. 

For a Category 1 submission, you should typically include a conclusion and a high-level summary (referred to as Section 1). Category 2 should include Section 1, as well as a description of intended device users and use scenarios (Section 2), a description of the device’s UI (Section 3), and a Summary of known use problems and use errors (Section 4). 

In addition, Category 2 submissions should also include an elaboration on why there aren’t any critical tasks, why no new critical tasks were introduced, and why there aren’t any changes that affect the pre-existing critical tasks for modified devices. 

Category 3 should include all the aforementioned Sections, in addition to a summary of preliminary analyses and evaluations (Section 5), an analysis of associated risks and hazards (Section 6), critical task analysis, identification and description (Section 7), and details of the human factors validation testing of the final design (Section 8).

How to Write a Human Factors Summary Report

The FDA’s guidance specifically states that the Administration is primarily concerned that the devices are safe and effective for the intended users and that the end goal is to ensure that the device’s UI is designed in a way that significantly reduces or eliminates any use errors that could potentially harm or degrade medical treatments. 

Unfortunately, the same document doesn’t explicitly state how to position or structure the Summary Report to clearly convey the various analytical results, which is a critical part of the success or failure of the report. In fact, anywhere between 70% and 90% of companies’ reports are rejected by the FDA due to a lack of human factors data. 

However, the FDA did include clearly defined basics that should constitute the report. The organization even issued a List of Highest Priority Devices for Human Factors Review, accentuating human factors’ importance in the agency’s review process. 

Include both quantitative and qualitative data in your report, as both can be used to convey the recorded observational performance of human factors and usability testing. For example, use charts with numerical data reflecting the participants’ use error rates. Then, back up this quantitative data with qualitative data. 

It’s important to list every detail during the development cycle of your device or combination product, including fail rates, user errors, and how said errors were addressed through a redesign. If one of the redesign iterations caused follow-on problems, prompting a subsequent redesign, include that as well. 

Think of it this way: for every possible aspect of your product, the FDA would want to know the “why” underlying a specific design feature. Answering that question without having the agency openly ask it is key to writing a successful report.


The results of human factors studies can significantly impact the regulatory strategy and submission timeline. Integrating human factors studies early in product development is often regarded as the best approach.