Processes, Techniques, and Tools: The 'How' of a Successful Design Control System

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI October 1997 Column

Cover Story: DESIGN CONTROLS

The new FDA emphasis on design controls has caused manufacturers to refine and formalize procedures that were, in many cases, simply unstructured.

Medical device manufacturers undoubtedly are now familiar with the requirements for design control set forth in the new FDA quality systems regulation. What is less clear, however, is how to best achieve design control, because the requirements give individual manufacturers lots of flexibility for implementation options. Three questions that need to be studied are: How does a company analyze what additional processes are needed to satisfy the design control requirements? How can a design control system be effectively implemented and integrated? and Which tools and techniques should be used to implement the design control system? Manufacturers need to decide on a method, a general approach to solving or modeling a problem; a technique, which is the way that problem will be solved; and a specific tool or step taken to implement a technique.

Manufacturers can use optical comparators like the one shown here to aid in their quality design control process (Johnson Matthey, West Chester, PA).

BACKGROUND

Scheduled to take effect June 1, 1998, the new quality system regulation governing medical device production is the first revision to good manufacturing practices in the past 19 years. This revision's primary goal is to harmonize the GMPs with the ISO 9001 quality certification standard, which will enable medical device companies to satisfy both sets of requirements with a single quality system. Design control is the second goal of the GMP.

The design control process in the medical device manufacturing industry has evolved backwards. Early quality control involved testing the finished product for defects, which was inefficient, potentially destructive, and expensive. The quality movement recognized this inefficiency and implemented manufacturing for quality through process validation. Controlling the manufacturing process prevents many defects that previously would have been caught only through inspection of the finished product. However, complaint files indicated that too many devices didn't produce the desired results, operate the way they were intended to, or meet safety standards.

Design controls address user needs and desires, including safety and efficacy, early in the design process. A study of device recalls indicated that a significant number of device failures (about 44%) were caused by design defects. Experience in various manufacturing and software development industries led to the formulation of the "1-10-100" law, which states that every product flaw identified in the design process can be corrected at 10% of the cost of a flaw that is not identified until the product is being manufactured; every flaw identified during the manufacturing process can be corrected at 10% of the cost of a flaw that is not identified until after the product has reached the market. The ratios may not be exact, but the point is valid.

As stated in section 820.30 of the regulation, the design control requirements are broad. The section is less than 1000 words long and is intended to be flexible enough to apply to every manufacturer of Class III and II­and some Class I­devices. Much has been written and spoken about what design controls require. Good sources include HHS Publication FDA 97-4179, Medical Device Quality Systems Manual: A Small Entity Compliance Guide, which has a section on design controls. The Quality System Compendium, published by the Association for the Advancement of Medical Instrumentation, addresses some of the practical aspects of design control, including subsections on industry practice. Design Control Guidance for Medical Device Manufacturers from CDRH is essential to interpreting the regulation and implementing a satisfactory design control system. In addition, FDA, in coordination with industry, has offered a number of design control training seminars nationwide.

ESTABLISHING, DEFINING, OR REFINING A DESIGN CONTROL SYSTEM

Before a design control system can work, the project must have management's support. Because a formal design control system is a different way of thinking about the design process, it often initially meets some resistance. Therefore, the first step in implementing a design control process should be education and training for the key people from management, marketing, sales, engineering, manufacturing, quality assurance, and configuration management, beginning with a common understanding of what design control involves, its benefits and problems, and the FDA requirements.

The design control process will be part of the larger design system already in place. Various designations of this larger system include the new product introduction process and product development planning process. In her book, Product Development Planning for Health Care Products Regulated by the FDA, Elaine Whitmore describes both strategic and tactical aspects of developing a new product, ranging from future-oriented activities such as technology forecasting and technology assessment to current activities of portfolio management of potential new products to actual product development. The book presents a rational approach to selecting new products for development and prioritizing product development projects.

Medical device manufacturers range from those that have already implemented a product development model that incorporates many, if not all, of the elements of design control to those that have no formally defined process. The challenge is developing a tailored design control process that makes sense for the company. Current processes should be reviewed to determine what design control elements are already in place. In some cases, a mapping of vocabulary may be sufficient. For example, one company conducted frequent reviews of the product development process and called them peer reviews. These peer reviews substantially satisfied the intent of design controls' design reviews.

A gap analysis can be used to review the existing system, and the Final Design Control Inspectional Strategy can be used as a checklist. If possible, an independent person or group should conduct this gap analysis. If an established model of a design control process isn't already in place, the initial goal should be to establish a repeatable process­a process that will allow the company to use the same procedure for both existing and future products, adding tasks and deliverables as necessary.

Making the process efficient or capable is the next­or possibly concurrent­step. The simplest way to describe the process is to break it up into a number of subordinate processes and relate them through process inputs and outputs. Some prefer to break up the process using the terms from the regulation: design and development planning, input, output, review, verification, validation, transfer, changes, and design history file. Others are more comfortable with the terms rapid prototyping, rapid development, rapid application development, spiral development, or concurrent engineering. Either way, every process described should have inputs and outputs, and the major functions or key processes identified through the process modeling exercise should be supported by standard operating procedures (SOPs). These can be individually designed, though there are commercially available SOPs that can serve as a starting point.

The easiest method for describing the design control process may be with a pencil and paper, creating a flowchart of tasks and activities with their inputs and outputs. Inputs may include feedback loops from other parts of the process to add functionality or correct problems in the system. For a simple process, this informal approach may be the best.

A technique of process modeling applicable to developing a design control model is Integration Definition for Function Modeling (IDEF0). This standard was developed by the U.S. Department of Commerce for displaying graphic representations of a process, system, or enterprise. The primary objectives of IDEF0 are as follows:

IDEF0 forces a measure of standardization and discipline into the modeling process. Many manufacturing industries use this as a standard because of its success record.

Software tools that run on all common platforms are available for automating the process description process. Several incorporate IDEF0, IDEF3 (process flows), and activity-based costing (ABC). These tools can be used for modeling the design control process. Some tools can launch applications and associated templates from the process model. By clicking on the appropriate activity rectangle or input/output arrows, templates can be brought up for the indicated process. For example, by clicking on a project plan document output, a template for the project plan will be displayed.

There are many other good process description techniques. A workbook, Mapping Work Processes, outlines the steps for teams and self-directed work groups to use in creating detailed flowcharts of existing processes. Also included are instructions on how to document work processes, which is a requirement for ISO registration.

Whatever technique is used to describe the design control process, the process will need to be reviewed and modified periodically to keep it effective and efficient. An established process should include all of the specified elements in subpart C of the quality systems regulation, beginning with design and development planning.

DESIGN AND DEVELOPMENT PLANNING

Three techniques are mentioned as project management tools in FDA's Design Control Guidance for Medical Device Manufacturers: program evaluation and review technique (PERT), the critical path method (CPM), and the Gantt chart. While these techniques can assist in project management, they do not completely satisfy the design control requirement for plans. For example, the design control inspectional strategy looks for descriptions or references and responsibilities for each of the elements of design control, as well as risk analysis and interfaces, but PERT, CPM, and Gantt are primarily scheduling and resource tools and would be unlikely to contain explicit information on organizational structure and responsibilities. Nevertheless, using these techniques encourage managers to think about all aspects of planning. Project management is essentially the planning, organizing, and managing of tasks and resources toward a defined objective. Three phases of project management are: (1) planning the project and creating a schedule; (2) managing changes; and (3) communicating project information.

A simple project probably doesn't require any tools other than paper and a pencil to implement the project plan. Simply list events, activities, milestones, estimated time to complete each activity or event, and the people or other resources that will be involved in the project. For more complex projects involving interactions that are hard to calculate or visualize, consider using commercially available software tools.

Look for tools that produce PERT and Gantt charts and generate the critical path. Some intuitive tools make identifying, scheduling, staffing, and monitoring design activities easy. Other desirable capabilities include allowing definition of tasks, supporting multiple task relationships, adding people and equipment resources to tasks, assigning costs to tasks and resources, allowing evaluation and adjustment of schedules, and providing a wide variety of progress reporting options for management. Project management tools range from the simple to the comprehensive, and thus complex. Experience has shown that simpler is usually better.

DESIGN INPUT

According to Design Control Guidance for Medical Device Manufacturers, "development of a solid foundation of requirements is the single most important design control activity." The design input section of the design control requirements is about establishing procedures to "ensure that design requirements are appropriate and address the intended use of the device, including the needs of the user and patient." But how can these needs be determined?

Sample process-flow diagram used for design planning.

Important sources include personnel from marketing, sales, customer training, and service and repair. They can provide customer input and complaints, warranty repair statistics, and service repair records, as well as information on any potential or pending lawsuits. Other sources include conventions, trade journals, trade shows, vendors, suppliers, academic institutions, government regulations, and standards organizations. More formal methods of obtaining requirements include focus groups, customer surveys, market surveys, and preferred customer surveys. Surveys can be conducted electronically, by telephone, in person, or by mail. Focus groups­discussions with small groups of participants­are a rich source of information, but their results may not be applicable to all customers.

It is important to identify the intended use of a medical device and examine the needs of the user and patient. An iterative process may be needed to clarify requirements and to provide the detail necessary for actual design. The biggest error in the design input process is not putting enough time and effort into obtaining a complete and unambiguous list of requirements. A recent study by the Standish Group, a well-respected market research firm, showed that the top three reasons why software projects were impaired were lack of user input, incomplete requirements and specifications, and changing requirements and specifications. These three answers accounted for 36% of the responses. The numbers may vary somewhat regarding medical devices, but the procedural problems are the same.

Capturing design input in a requirements database and assigning attributes can be done using computerized statistics programs (Incorp.=incorporated).

One difficulty is identifying design input; managing and tracing the steps from design input through design output, verification, validation, and design transfer is another challenge. There are techniques and tools to help solve both of these problems. A good database or spreadsheet program is an excellent tool for managing and tracing design input. For projects of intermediate to high complexity, the technique Quality Function Deployment (QFD) and a generic set of tools known as requirements management tools can be the answer.

QFD was developed in Japan in the late 1960s in an effort to get engineers to consider quality early in the design process. It expanded and implemented the view of quality as advocated by quality guru Deming, and it was embraced by the Japanese automotive industry. Toyota partially attributes its success to QFD, which reduced both its development time and the number of required change orders after production was started. Because of QFD's success in Japan, automotive-related training organizations started teaching it in the United States. It has since spread into many nonautomotive industries, including the medical device industry.