Efficient Test Protocols Eliminate Cost and Complexity

When a medical device company outsources the design and manufacture of its device, it wants to ensure that the firm’s outsourcing partner a) builds the right thing, and b) builds it right. To meet customer requirements and performance specifications, it’s essential to create test protocols that give detailed instructions for what was tested, how it was tested, why it was tested, and when it was tested. This, however, often is easier said than done.

To sufficiently verify and validate that a device will operate safely and reliably from its first through 1,000th use, test protocols must consider a device’s entire life cycle. And in the competitive world of medical devices, it’s also important for test protocols to be as efficient and effective as possible in order to accelerate time to market.

With all these different considerations, it’s understandable how certain testing parameters can get over-analyzed—or even overlooked. Nonetheless, the repercussions of doing so are considerable. Ineffective test protocols can delay product release, add significant cost to the project, and even cause the device to fail in the field.

By adhering to a few dependable strategies, the process of creating test protocols can be simplified to minimize complexity, time and cost. The following tips are intended to help design teams avoid unnecessary testing, shorten the development cycle, prevent nonessential spending and, most importantly, increase customer satisfaction.

Communicate, Comprehend and Collaborate
Test protocols are only as good as the customer specifications they are based on. If the design team is unclear or uncertain about what the customer wants and needs, protocols that test performance, safety, functionality, and reliability will likely be inaccurate—or even omitted.

To develop effective and efficient test protocols, it’s imperative to assemble cross-functional team members for the initial customer meeting. Involving multiple points of view and backgrounds in the discussion as early as possible enables all the team members to consider different variables related to how the device will be used and the environment in which it will be used. This helps bring potential issues to light before they happen and allows the design team to refine what test protocols are established.

For example, if the customer communicates that the device will be released in Europe, having the expertise of the regulatory affairs and quality assurance (RA/QA) team will ensure that European sterilization requirements are accounted for in the testing process. As a result, the design engineer can create more rigorous protocols to test how well the device’s design, materials, performance, and fixtures hold up to higher pH levels.

Early communication and cooperation between the customer and the cross-functional team supports productive test protocols, reduces costly, time-consuming testing redundancies, and inhibits failures.

Produce Prototypes
More often than not, customers approach a design and manufacturing partner with a vague idea of what they want and need from their medical device. They may need their device to contain a motor with 60 in./oz. of torque, but they want it to be the size of a Sharpie marker. A design engineer intrinsically may know that the customer’s torque request is overkill for what is really needed. But instead of trying to verbally explain why or illustrate the point from a CAD drawing, it often is more constructive to show the customer a functional prototype of what they are asking for.

A functional prototype is a bare-bones, primitive model of the customer’s design specifications. Because the customer can see and feel the prototype, it makes it easier for them to understand why a Sharpie-sized device can’t accommodate a particular torque. Prototypes also can guide discussions about alternative solutions and foster compromise between what is wanted and what is actually needed.

The sooner the product parameters are nailed down between the customer and the product development team, the faster the engineer can create test protocols that adequately verify and validate the device’s safety and reliably.

Experiment
Once the device’s design specifications have been set and approved by the customer, control limits must be established. Control limits (also called process limits) are used to determine whether or not a manufacturer’s production process is operating at its full potential to produce a conforming product.
Determining control limits can require some trial and error, which is where Design of Experiments (DOE) comes in. DOE is a tool that takes into account multiple variables simultaneously, as well as statistical analysis, before test protocols actually are written and carried out.

Evaluating multiple variables at the same time, versus evaluating one variable at a time while all others are held constant, reduces the number of design iterations required to develop a safe and reliable device.

For example, a design engineer who needs to write the protocols for testing the sealants in a powered surgical device while it’s in an autoclave might conduct a DOE to evaluate how various temperature, time, and pressure limits affect the strength of the seal. (See Figure 1.)

“A DOE approach permits efficient use of resources (personnel time, machine time, materials, etc.), provides detailed analysis, gives information on reproducibility and errors, and provides a predictive capability. Applying DOE reduces the size and hence the cost of process validation trials,” according to the article“Application of Design of Experiment Techniques to Process Validation in Medical Device Manufacture.”¹

In addition, DOE makes it possible to catch “out of control” processes even before non-conformances arise, leading to further reduction in the cost and time required to produce the device.

Take Time
Time is of the essence when it comes to designing and manufacturing medical devices. However, when it comes to developing comprehensive, accurate test protocols, there are situations that require testing methods that may take more time, such as performing sterilization tests between every functional test.

Because it takes longer to test a device’s functionality while simultaneously analyzing how it holds up in harsh sterilization environments, some testers separate these testing methods to try and accelerate the process. Unfortunately, this can cause important variables to get overlooked.

For example, if a test protocol only requires a tester to sterilize a device hundreds of times in the autoclave without turning it on between cleaning cycles, the protocol isn’t taking into consideration that the device likely will be used again after it’s sterilized. Alternatively, a test protocol that only advises the tester to run the device 500 times to test its performance isn’t accounting for how the motor, seals and internal components will function after being exposed to moisture in the autoclave.

It’s crucial to conduct component and subsystem tests early in the development phases—long before a completed product. Component-level testing analyzes individual aspects of the device where subsystem tests bring together different components to see how they interact with one another. A component-level test might involve testing the motor separately to determine its limits and ensure that it functions properly before it’s put into the full system.

Once the motor is tested using realistic testing parameters, adding another variable (a cable, for example) allows the tester to evaluate how the two interact. If the two variables interact successfully, the next step would be to add another component to the test (e.g., a seal). If the motor and cable test well together, but an issue or a failure arises when the seal is added, it indicates that the issue must be caused by an interaction between the motor and cable, and not the individual component.

Testing each subsystem before it goes into a complete system helps eliminate redundant testing and prevents unintended consequences that could make the entire device fail in later testing phases. Ultimately, this accelerates the process of verifying and validating that the entire device will be able to handle the rigors of field use.

* * * 
Gaining a clear, consistent understanding of the customer’s specifications and the device’s intended field use is the foundation for creating thorough, effective test protocols. Conducting DOE, performing functionality and sterilization tests and carefully evaluating components and subsystems, builds on that foundation to create testing protocols that account for all the components involved in a product.

While developing test protocols is not a one-size-fits-all approach, taking these approaches into account can help prevent pertinent tests from being overlooked and streamlines the verification and validation process so that it is as efficient and cost-effective as possible.

---

References:
1. D Dixon et al., “Application of Design of Experiment (DOE) Techniques to Process Validation in Medical Device Manufacture,”Journal of Validation Technology 12, No. 2 (2006).

---

Daniel Santos is the engineering manager at Pro-Dex Inc., a publicly traded Irvine, Calif.-based company that designs, develops and manufactures powered surgical devices, air-motors, metal components, and sub-assemblies for world-class medical device OEMs.