Medical devices are crucial since they directly impact human lives. Medical device manufacturers must follow testing, verification, and validation best practices to ensure quality and reliability of medical equipment in order to provide safe and effective healthcare services to patients. Here is a high-level overview of implementing medical device testing strategies.

Multiple regulatory bodies and compliances govern the medical devices. On the other hand, the end users expect exceptional performance, effectiveness, and safety from the device that they use. This compels the medical device manufacturers to create and deploy medical device testing strategies that work across the development cycle — from concept and design to production.

A medical device testing strategy must include both compliance processes and technical testing methodologies for better performance and effectiveness of the medical devices. The manufacturers should have a robust testing plan in place right from the beginning of the design process, as exhaustive testing of a finished product is ineffective and inefficient.

For e.g. for improved test coverage, a manufacturer must test each functionality of the medical device starting with the design stage. This ensures cost and time effectiveness which is difficult to achieve when the manufactured devices are tested.

Devising an effective medical device testing strategy

The testing team should consult the design team as a source of knowledge. Design input can help to derive the test structure that matches the hardware, software or other technical requirements. To determine the device’s test needs for risk mitigation, the design classmodes, effects, and criticality analysis (FMECA) can be utilized.

An effective medical device testing strategy needs several sets of test requirements.

These test requirements are based on the device’s component specification, the manufacturing process, and other critical functional specifications. The test requirements define and describe the setup conditions, the actions, and the expected response constraints for each experiment defined in the test steps.

These sets of requirements are needed to make the test implementation easier as the tests are carried out continuously at various stages of the entire manufacturing process, from component selection to final assembly of the medical device. Each stage has its own set of requirements and parameters to meet.

Applying medical device testing strategy

Production testing of components, sub-assemblies, and the finished product is included in the highest level of medical device test strategy for technical testing. The test strategy considers specific hardware and software requirements for each test stage, as well as the measurement methods and the expected output.

An effective test strategy is a product level activity that takes into account a complete test set at every step of the product development process. It analyses and correlates faults in a test model to improve the device’s overall performance. The strategy defines the desired output for each stage to ensure overall efficacy. The system is broken into small blocks during the validation process, to maintain traceability to the original test strategy, and then the testing begins with specific criteria for each block in the system. Each block’s validation methods are tailored based on the risk-based analysis to better match the test strategy. The high-level test strategy provides a strong reference for the device’s technical reviews and its validation.

Microprocessor testing

Medical devices must undergo rigorous electronic testing in order to meet the highest quality standards. Most of the class II and III medical devices have microprocessors at their core. Hence, microprocessor evaluation is the first step in medical device testing. Access to the transistors’ interconnections within a microprocessor is necessary for effective testing. However, for enhanced testing efficiency, the testing team should test the microprocessor’s chips before inserting them into a Printed Circuit Board (PCB).

The integrated circuits are subjected to tests that look at their logic gate functions and how they’re connected. Based on the requirements, suitable techniques are selected from a variety of industry-standard test methods.

Once all the components have been attached to the PCB, comes the testing of mounting and the interconnection process. Throughout this phase, the testing team uses a common assembly defect model to discover the wrong component, the missing component, open interconnect, shorted interconnect, and other issues in the PCB assembly process.

Modern test equipment provides physical access to the PCB and allows direct measurements of components in small groups. It is important to ensure that these small groups of components in the PCB do not affect the system’s functioning as a whole. Hence, functional testing is essential for all the functions that are influenced by the other components’ parameters. Functional testing allows similar PCBs but they are insufficient for finding common manufacturing flaws. Therefore, additional troubleshooting is required to identify specific repairs.

Automating the test

A test automation system is an electronic system that comprises a computer, instruments, and software for carrying and controlling the testing process. Certain commercial test automation systems are available in the market in accordance with the industry standards. However, the testing team may use a customized test system based on their needs.

The testing team may need to adjust the strategy based on the available test alternatives for each step of medical device development. It may pose restrictions for the testing team by limiting the implementation techniques.

The testing team may face challenges in the test automation environment while testing complex medical devices with severe voltage and current needs. This is due to the limited ability to develop the test cases and to measure the test’s accuracy.

Ideally, automated test implementation is a matter of simultaneous hardware and software design. The test set for a certain stage in the manufacturing process flow is determined by the specifications assigned to that particular stage in the test strategy. We must break down those test specifications into software and hardware requirement specifications according to the test system software and interface hardware, respectively.

System specifications are often derived from the medical device design stage, but certain requirements such as security and data integrity must be derived from the production test environment. All of those standards result in the mechanical design, the coding and the electrical design of the test system. Common blocks of hardware and software are re-used to streamline the process in an established facility where multiple medical devices have been designed, built, and tested.

Validation process

Once everything is in place, the medical device test system must be validated, including software and hardware. The process of software and hardware validation for medical devices is detail specific. The purpose of validation is to test whether the device meets the specific user needs or not. Hence, the structure and the approach are pivotal to apply the validation methodology.

Validation is carried on the first production unit. In other words, a validation device is integrated into the production environment. The process involves the end-users and is tested under simulated use or under the actual use. Validation tests are necessary to ensure that the medical equipment works as intended and meets its users’ needs.

The initial approach for validation starts with unit testing of a set of stages in the process and then a complete system is validated. Given the system’s complexity, most automation systems find validation challenging. In that case, a divide and conquer validation approach is better.

Integration testing of the entire system is a vital technique, but it should be the result of a coordinated validation protocol rather than the entire plan.

A medical device’s functional testing entails the evaluation of various functional blocks, such as the operating system, the instruments, and the hardware, among others, all of which must be validated for their intended purpose. The process starts with the manufacturer’s specifications or a subset of specifications from the design and the test team, and these can be applied to each block.

The testing team should collaborate with the manufacturing team to validate those specifications, and then test and verify the performance of each block to document the results and review them. The functional block test comes handy for validation of the custom developed medical devices’ hardware or software.

Verification testing

Verification is the process of confirming that the device’s defined requirements have been met through examination and provision of the objective evidence. The verification process starts with clear and well-defined product requirements that must be measurable for verification. We must know the answer as verification is not an experiment.

The process follows several formal protocols. It suggests comparing the current product’s requirements with those of the already approved products. The verification process must contain the full methodology or a reference to a standard methodology, a statistical justification for sample size, a statistical plan for data analysis, and more. It should also specify the acceptance criteria details and the procedure to follow in case of failed verification.

If the verification fails, a deeper investigation is needed to determine the requirement that could not be verified and whether or not it is valid or doable in the existing design. This further investigation may reveal whether the product requirement can be updated and re-verified.

A well-defined and implemented medical device testing strategy can help manufacturers save money while also ensuring that their devices meet the end users’ expectations. It also lowers the chances of a device recall. Collaboration with businesses that have domain expertise in testing is recommended from a business standpoint since it reduces the overall risk and the testing time.

eInfochips has been an innovation partner for many medical device companies, including Fortune 500 firms. We have experience throughout medical devices lifecycle stages, namely product ideation to design and development, component engineering, product re-engineering, testing and verification and validation, sustenance engineering, and regulatory compliances.

For more details, download the success story of a California based medical device company for which we developed a portable, battery-operated insulin pump with a software controlling dosage. To know more about our services, please contact us today.