ISO 10993: Biological Evaluation of Medical Devices, Explained

ISO 10993 is the multi-part standard for the biological evaluation of medical devices, usually shortened to biocompatibility. Part 1 is the framework and the part you start from; the numbered parts under it cover individual endpoints and methods.

ISO 10993-1 describes a risk-based evaluation rather than a test checklist. You test when the evaluation cannot answer a question from information you already have.

Contact type and duration set the endpoints

The framework categorizes a device on two axes, and the pair determines which biological endpoints need addressing.

Nature of body contact:

• Surface devices: intact skin, mucosal membranes, or breached surfaces
• External communicating devices: blood path indirect, tissue/bone/dentin, or circulating blood
• Implant devices: tissue/bone, or blood

Duration of contact:

• Limited: up to 24 hours
• Prolonged: 24 hours to 30 days
• Long-term: over 30 days

Duration is cumulative. A device used for an hour a day over a month is prolonged or long-term contact, not limited.

The endpoints

Depending on category, the evaluation addresses some subset of: cytotoxicity, sensitization, irritation or intracutaneous reactivity, acute systemic toxicity, material-mediated pyrogenicity, subacute and subchronic toxicity, genotoxicity, implantation effects, haemocompatibility, chronic toxicity, carcinogenicity, and reproductive or developmental toxicity.

Cytotoxicity, sensitization and irritation apply to essentially everything. The rest scale with contact and duration.

Addressing an endpoint does not mean testing it. You address it with whatever evidence answers the question: chemical characterization, published literature, data from an equivalent material with the same processing history, or a test.

Chemical characterization comes first

ISO 10993-18 chemical characterization, feeding a toxicological risk assessment under 10993-17, is the front of the process rather than an alternative to it. You characterize what can come out of the device, assess whether those constituents present a risk at the exposure your device produces, and test only where that assessment leaves a question open.

Running the full battery first is slower, more expensive, uses more animals, and frequently answers questions the chemistry had already closed.

FDA expectations

FDA recognizes ISO 10993-1 with its own guidance, and the guidance matters as much as the standard. These points recur:

Your evaluation is of the final, sterilized device, in its final configuration, with its actual manufacturing and processing history. Data on the raw material is not data on your device. Sterilization, cleaning agents, mould release and adhesives all change the answer.

A change in material, supplier or process reopens the evaluation. That means a documented assessment of whether the change affects the biological risk, and not automatically the whole battery.

Common failures

• Testing before characterizing, which is often unnecessary.
• Evaluating the material rather than the device. The device is what contacts the patient, after everything you did to the material.
• Contact duration understated. Cumulative, not per use.
• Supplier change treated as a purchasing decision. A different resin from a different plant is a biocompatibility question.
• Equivalence claimed too loosely. Relying on data from a similar device requires demonstrating the same material, processing and contact; the same product category is not enough.
• No link to the risk file. Biological risk belongs in the ISO 14971 risk management file like any other, and an evaluation that lives only in a test report is disconnected from the device's overall residual risk.