FDA publishes draft guidance on testing medical devices

The US Food and Drug Administration (FDA) wants medical device sponsors to test products that may cause changes in tissue temperatures, regardless of whether they heat or cool the tissue and whether the change in temperature is intentional. The agency provided details on how to conduct testing and gather data, and recommended sponsors talk to regulators early.

On 15 March, FDA published a draft guidance outlining the agency’s recommendations for conducting testing, gathering data, and presenting results in premarket applications to reviewers on medical devices that may cause tissue temperature changes.

“[FDA] is issuing this draft guidance document to describe relevant information that should be provided in a premarket submission (i.e., premarket approval (PMA) applications, humanitarian device exemption (HDE) applications, premarket notification (510(k)) submissions, investigational device exemption (IDE) applications and De Novo requests) to support the evaluation of thermal effects of medical devices that produce local, regional, and/or systemic changes in tissue temperature (i.e., heating and/or cooling) due to their use,” said the agency. “The recommendations in this guidance reflect current review practices and are intended to promote consistency and facilitate efficient review of thermal effects data for these devices.”

“Where available, device-specific guidance documents and/or standards may include additional technical recommendations on thermal effects evaluation that should be considered,” the agency added.

FDA listed several types of medical devices that may need to undergo tissue temperature testing, including those that deliver radiofrequency, microwave, light, or other forms of electromagnetic energy, as well as those that deliver ultrasound, and electroporation devices. The agency said devices that produce temperature changes from contact with tissue, such as hyperthermia, high-temperature ablation, hypothermia, and cryoablation, and those with components that may produce such reactions, also fall within the scope of the guidance.

“An evaluation of thermal effects should include verification of device parameters and an assessment of tissue effects (e.g., thermal damage, tissue appearance, tissue/organ function) and related spread of thermal energy,” said FDA. “An assessment of tissue effects and thermal energy spread may be performed experimentally (i.e., using phantoms, ex vivo animal tissue models, and/or in vivo animal testing), computationally, and/or clinically.”

FDA recommended sponsors assess tissue effects and thermal energy spread from their device before verifying it meets its labeling parameters. To verify labeling parameters, the agency recommends they provide benching data on the full range of its specifications and added that the testing should have pre-defined acceptance criteria based on its use conditions.

“If the testing results in deviations from the acceptance criteria, you should provide a scientific rationale to support device safety and effectiveness for the specific use conditions,” said FDA. “This verification testing is important to demonstrate that the data generated on tissue effects and thermal energy spread are appropriately representative of the final finished device’s performance.”

o assess tissue effects and thermal energy spread, FDA lists experimental models that sponsors may consider, including phantom testing, ex vivo animal tissue testing, and in vivo animal tissue testing. The guidance also addresses issues such as tissue testing methods, measuring regions of tissue that have been thermally affected and how they spread, and reporting those findings to regulators.

Sponsors are encouraged to contact the FDA through its Q-Submissions Program to seek early feedback on their approach and study design when developing a strategy to evaluate their devices for thermal effects. The agency also recommended they review its guidance on the Q-Sub program.

“In addition to labeling requirements and recommendations from any relevant regulations or statute, and device-specific guidances, we recommend that you include a chart and/or graph in your labeling that provides the dimensions (i.e., length, width, depth, and volume) of the thermally affected tissue region in relation to the power setting, and duration of activation for different tissue types,” said FDA. “This information is important to inform users of the expected damage and to facilitate safe use.” RAPS.gov