Improving Patient Outcomes in the Development of Medical Devices: The Importance of Human Factor Testing

Tue, 03/11/2014 - 12:28pm
Raza Ahmed, MD, Worldwide Director, Medical Affairs, BD Medical-Pharmaceutical Systems, and Corinne Granger, MD, Vice President, Medical Affairs, BD Medical-Pharmaceutical Systems

Human Factors Engineering (HFE)—the process of designing equipment and devices that fit the human body—involves a multidisciplinary approach with contributions from biomechanics, engineering, industrial design, economic theory, human performance, graphic design, research and development, psychology, and clinical research. The working philosophy of HFE is now being utilized in the pharmaceutical industry to address many of the drug delivery needs for patients with chronic medical conditions such as diabetes mellitus, multiple sclerosis, and rheumatoid arthritis, where self-administration of medication is desired. Improving patient adherence to long-term therapies is now a major requirement for achieving optimal treatment efficacy and expected therapeutic outcomes.1,2 Studies demonstrate that self-administration of medication can increase patient treatment adherence and reduce cost by decreasing the frequency of hospital visits, benefitting patients in terms of cost, time, ease of use, improved self-esteem and greater independence.3,4 Using an interdisciplinary development approach that evaluates patient dynamics and focuses on improving the safety, efficiency, and robustness of the delivery system, HFE has revolutionized the lives of these patients.

In the development of medical devices, including self-administration devices, HFE focuses on addressing an array of individualized aspects of device design and patient utilization (Figure 1), including:

  1. Task analysis and design
  2. Device evaluation and usability
  3. Patient acceptance, compliance, and adherence
  4. Anticipated training, education requirements, and validation of instructions for use
  5. Systems resilience, adaptation, and failure

Figure 1: Process Map for the Assessment of Human Factors in the Development of Medical Devices5

Human factors testing is now critical in the regulatory assessment of medical devices, as it validates the overall patient usability of the design system including safety, efficacy, usability, and risk.

Testing of Human Factors
The testing methodology for evaluating human factors is dependent upon the patient characteristics under evaluation. Human factor testing is often initially conducted using a small number of test participants (n~15) with initial prototypes and product labeling (including the draft instructions for use). This initial testing enables multiple minor modifications and evaluates them in an iterative fashion until the device is considered optimized to a level at which formal, larger-scale validation testing with prototypes is appropriate. Human factor testing then moves to more rigorous, validation-based testing in target populations (n~25).

The formative validation testing should first focus on the major issues identified during the preliminary evaluations phase — factors considered most likely to impact the overall use, safety, and effectiveness of the device, as well as areas where design options are incomplete. The evaluation methods should be chosen based on the need for clarification prior to developing final design specifications. Ideally, formative validation testing of human factors will address the following goals:

  • Guide modifications of the design to maximize overall patient experience
  • Identify potential use-related hazardous situations leading to the development of risk mitigation strategies
  • Evaluate trade-off scenarios specific to the effectiveness of design enhancements, device training, and instructions for use
  • Guide the development of field-based use scenarios for subsequent design validation testing

Successful formative validation enables larger-scale, field-based testing to proceed, with few or no user difficulties or concerns.

Potential Limitations to Human Factors Testing
Field-based survey methods are useful because they enable testing in patients’ natural environment. Limitations to HFE testing do exist, however,6 testing requires a substantial investment in planning, recruiting, and execution, and highlights potential issues related to recruitment, training, and monitoring. Study periods may be longer to accommodate the redesign of the medical device, possibly resulting in increased patient attrition.

Many HFE studies are conducted in simulated environments and require follow-up within the context of a clinical trial. In addition, a validated questionnaire is needed to assess patient acceptance of new devices in the context of different disease therapies. Presently there are few questionnaires available for comparison between studies using the same device for different diseases able to assess patient acceptance based on the disease.4,7

Several questions must be addressed to ensure any “negative” outcomes are driven by physical ability rather than emotion or opinion. How much time is needed to learn the use of medical device, independent of human factors testing? Are identified errors related to the unintentional misuse or an inherent design fault of the medical device? To what extent do cognitive abilities overshadow physical abilities in the utilization of the medical device? To accurately assess patient acceptance, the physical and cognitive capability of patients must be assessed, though validated questionnaires capable of such characterization are limited.

Guidance on the Use of Human Factors
The Center for Devices and Radiological Health (CDRH)  at the U.S. Food and Drug Administration issued draft guidance on the utilization of human factors in medical device development and testing in June 2011.7 Designed to assist industry in human factors testing and device features that should be optimized throughout the product life cycle, the recommendations are intended to improve the usability of devices to reduce user error, injuries from medical devices, and product recalls, as well as to help control current and future risks associated with device use.

The Association for the Advancement of Medical Instrumentation (AAMI) in conjunction with the American National Standards Institute (ANSI) published a recommended practice covering HFE principles for mobile medical devices and home health care devices.9 This document emphasizes the need for HFE design and testing to account for the environment in which the medical device will be used and user needs, capabilities and expectations. The CDRH also issued a draft guidance for design considerations for devices specifically intended for home use.10 Additionally, HFE studies must consider the needs of the targeted patient population or their caregivers. The CDRH issued a draft guidance for pediatric uses for medical devices, and the AAMI recommended practice offers guidance for patients with disabilities.9,11 Additional studies focus on disabilities relating to specific disease states.

Human Factors in Action
BD (Becton, Dickinson and Company), a leading medical technology company, has over 100 years of experience developing medical technologies to address healthcare problems, with a patient-centric device development culture that informs and inspires the current product design approach. In developing or modifying a self-administration system, BD engineers undertake extensive patient-focused research designed to uncover unmet patient needs, identifying human factor concerns that directly impact usability. The goal of each product development team is to develop drug delivery systems that make it safer and easier for patients to take medication correctly and consistently. Multiple rounds of usability testing are integral to this process, which places the system in the hands of target users.

Human Factor Testing in the Development of BD’s Self-Administration Devices
Designed for use in the treatment of chronic diseases such as rheumatoid arthritis, multiple sclerosis, and osteoporosis, the BD Physioject disposable autoinjector is a single-use, disposable autoinjector that incorporates the 1-mL BD Hypak glass prefillable syringe to perform automatic injections in fixed doses. During its development, multiple human factors studies were undertaken to evaluate all aspects of performance safety, efficiency, patient acceptance, and ease of use, including pain perception versus prefilled syringes. Initial studies assessing performance, safety, and efficiency conducted in healthy volunteers indicated that the BD Physioject disposable autoinjector is able to safely inject the correct volume and offers less pain and improved user acceptance.12 Additional studies by patients with rheumatoid arthritis including patients with severe hand disability, demonstrated high patient acceptance for self-injection.13 A specific human factors initiative was undertaken to evaluate the impact of typeface and fonts on the usability and patient perception of the BD Physioject disposable autoinjector. When designing the BD Vystra disposable liquid pen, height of the dose font significantly impacted the distance from which the dose window could be viewed (Figure 2). Viewing was also impacted by font color, lighting conditions, line of viewing, and overall patient eye condition. Incorporating these human factors into the final development of BD’s self-administration devices has enabled greater utility in a wider patient population. Favorable ratings for convenience and ease of use of an autoinjector for self-administration of injectable therapy for patients with multiple sclerosis were confirmed in a clinical trial.

Figure 2. Assessment of Human Factors Related to Visual Acuity in Disposable Drug Delivery Pens

Human factor testing is now integral to the development of drug delivery systems including disposable pens, autoinjectors, and patch pumps. Through HFE, medical technology companies can design drug delivery devices that meet the physical and emotional needs of patients, healthcare providers, and other users - ensuring increased patient usability and therapeutic compliance. Human factors testing provide a patient-focused approach to the development of new and innovative strategies to meet the needs of the pharmaceutical industry, and addresses recent regulatory guidance regarding device design.


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8 Administration UFaD. Draft Guidance for Industry and Food and Drug Administration Staff - Applying Human Factors and Usability Engineering to Optimize Medical System Design. 2011(January 13, 2014). Accessed June 22.
9 ANSI/AAMI HE75. Human factors engineering-Design of medical devices. 2009 ed. Arlington, VA: Association for the Advancement of Medical Instrumentation; 2010.
10 Administration DoHaHSFaD. Design considerations for intended for home use. 2012.
11 Health USDoHaHSFaDACfDaR. Draft Guidance Pediatric Uses of Devices. 2013.
12 Berteau C, Schwarzenbach F, Donazzolo Y, et al. Evaluation of performance, safety, subject acceptance, and compliance of a disposable autoinjector for subcutaneous injections in healthy volunteers. Patient Prefer Adherence. 2010;4:379-388.
13 Schwarzenbach FT, M. D.; Grange, L.; Laurent, P. E.; Abry, H.; Cotten, J.; Granger, C.;. Results of a human factors experiment of the usability and patient acceptance of a new autoinjector in patients with rheumatoid arthritis. Patient Preference and Adherence. 2014 [in press].



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