Biocompatibility Testing for Medical Devices: What FDA Actually Requires and How to Get It Right

Biocompatibility Testing for Medical Devices: What FDA Actually Requires and How to Get It Right

If you are developing a medical device that contacts the human body -- even indirectly -- biocompatibility is not optional, and it is not an afterthought. It is one of the first things FDA reviewers scrutinize in a 510(k), De Novo, or PMA submission. Yet it remains one of the most misunderstood and mishandled components of a regulatory package. Sponsors either over-test (burning runway on studies that were never needed) or under-test (triggering an AI or major deficiency that delays clearance by six to twelve months).

This post breaks down exactly what FDA expects, how ISO 10993 translates into your submission strategy, and where teams most commonly get tripped up.

The Regulatory Foundation: ISO 10993 and 21 CFR Part 820

FDA does not have a standalone biocompatibility regulation in the CFR the way it does for, say, design controls under 21 CFR Part 820.30. Instead, FDA references a voluntary consensus standard: ISO 10993-1:2018, Biological Evaluation of Medical Devices -- Part 1: Evaluation and Testing Within a Risk Management Process.

The agency's primary guidance document is the 2023 FDA guidance: 'Use of International Standard ISO 10993-1, Biological Evaluation of Medical Devices -- Part 1: Evaluation and Testing Within a Risk Management Process.' This guidance is not aspirational. It defines FDA's current thinking and directly maps to what reviewers use when they assess your biocompatibility data.

Under the Quality System Regulation (21 CFR Part 820, now being harmonized with ISO 13485 under the Quality Management System Regulation), design controls require that design outputs -- including materials -- meet design inputs. Biocompatibility testing is a direct output of that process. Failure to document it properly is a design control deficiency, not just a biocompatibility gap.

The Risk-Based Framework: It Starts With Device Categorization

ISO 10993-1 organizes biological evaluation around two primary variables: the nature of body contact and the duration of that contact.

Contact categories include:

• Surface-contacting devices (skin, mucosal membrane, breached or compromised surfaces)
• External communicating devices (blood path indirect, tissue/bone/dentin, circulating blood)
• Implant devices (tissue/bone, blood)

Duration categories are defined as:

• Limited: less than 24 hours
• Prolonged: 24 hours to 30 days
• Permanent: greater than 30 days

These categories drive which endpoints from ISO 10993 Parts 3 through 22 are relevant to your device. The most commonly required endpoints include cytotoxicity (ISO 10993-5), sensitization (ISO 10993-10), genotoxicity (ISO 10993-3), systemic toxicity, and -- for implants or blood-contacting devices -- hemocompatibility (ISO 10993-4) and implantation studies (ISO 10993-6).

Here is what many sponsors miss: FDA does not require you to run every test. What FDA requires is a documented, scientifically justified biological evaluation that explains which endpoints are relevant, how you addressed them (whether through testing, literature, or existing data), and why your approach is sufficient given the device's risk profile.

The Biological Evaluation Plan and Report: Your Most Important Deliverable

Before any testing begins, you need a Biological Evaluation Plan (BEP). This document should identify all patient-contacting materials, map each to the appropriate ISO 10993-1 contact category and duration, identify applicable endpoints, and justify your testing or data-leveraging strategy.

After evaluation and testing are complete, you produce a Biological Evaluation Report (BER). The BER is what goes into your submission. FDA reviewers expect this document to be comprehensive, traceable to your risk management file (per ISO 14971), and authored or reviewed by someone with relevant toxicology and materials science expertise.

Submitting raw test reports without a BER -- or submitting a BER that does not connect endpoints to device contact categories -- is one of the most common reasons biocompatibility sections generate an AI (Additional Information) request.

Where Sponsors Get Into Trouble

Based on experience supporting 510(k) and PMA submissions across device classes, the highest-frequency failure points are:

• Using predicate device biocompatibility data without justification. Substantial equivalence to a predicate does not automatically transfer biocompatibility. You must show material equivalence or conduct independent evaluation.
• Ignoring processing and sterilization effects. FDA expects you to test final, finished, sterilized devices -- not raw materials. Sterilization can introduce residuals (e.g., ethylene oxide) that change the biological risk profile entirely.
• Inadequate chemical characterization. FDA increasingly expects a toxicological risk assessment (TRA) grounded in chemical characterization data per ISO 10993-18 before defaulting to animal-based testing. This is not just best practice -- it is now an explicit FDA expectation in the 2023 guidance.
• Misidentifying contact type or duration. A device used in a wound care application that contacts compromised skin is not the same as one contacting intact skin. This distinction changes your endpoint requirements substantially.

A Practical Path Forward

Start your biocompatibility evaluation at the same time you finalize your material selections -- not after design freeze. Retrofitting biocompatibility to a locked design is expensive and sometimes impossible without triggering a material change that restarts the clock.

Engage a qualified toxicologist early. FDA does not specify credentials, but reviewers notice when a BER lacks scientific rigor. If your team does not have in-house toxicology expertise, that gap needs to be filled before you submit.

Finally, treat your biocompatibility file as a living document within your design history file (DHF). Material changes, supplier changes, and sterilization method changes can all invalidate prior biocompatibility conclusions and require re-evaluation.

Work With an Expert Before You Submit

At ADB Consulting and CRO Inc., we have guided device companies through biocompatibility strategy, BEP and BER development, and FDA deficiency responses across Class I, II, and III devices. Whether you are early in development or staring at an AI letter, we can help you build a defensible, submission-ready biocompatibility package.

Book a free discovery call with Andre Butler today. Visit adbccro.com to schedule time directly. Let us make sure your biocompatibility strategy is one less thing standing between you and FDA clearance.