Biocompatibility: key questions

by | Aug 18, 2021 | MDR

Biocompatibility medical device

Read IMed’s Safety Assessment Strategy specialist’s guidance on biological safety, as Phil Clay kindly shares his expertise on both of the key recurring questions he’s always asked regarding biocompatibility.

When clients start thinking about the biological safety of their device, they often ask the following 2 questions; “I’ve got biocompatibility testing done, will that do?” and “Do I need an extractables and leachables study?” So – in that order, here are our answers;


Many device manufacturers have a collection of biocompatibility study reports for the device and safety data sheets for the materials.  Historically, simply adding this data to your submission to a notified body, would have been considered to be an assessment of the biological safety of the device.  ISO 10993 indicates that the process of biological evaluation should be ‘planned’ and that the biological evaluation plan should be drawn up by a knowledgeable and experienced team.  If any unacceptable risks are identified, then additional testing may be appropriate to complete the risk assessment. Very similar wording is included in guidance for most authorities around the world.  So – simply providing the assessor with a collection of information is no longer acceptable. You will be expected to demonstrate how and why these data show your device is safe, and also that the information has been evaluated by an appropriate, knowledgeable and experienced individual.  Many notified bodies will now reject any biological evaluation, which has not been written by a registered toxicologist (ERT or DABT).

Extractables and leachables study?

There is great focus now on “chemical information” as part of the biological evaluation of a device.  Table A.1 in ISO 10993/1, tells us that chemical information is prerequisite information for a risk assessment.  This has been widely (mis)interpreted as meaning that chemical analysis of extractables and leachables (E&L) is required for all devices.  Before jumping into a potentially expensive E&L study, you should pull together all the information you can on the materials and manufacturing process, as part of your biological evaluation plan.  ISO 10993/18 very clearly states that

‘if one can demonstrate that a hypothetical exposure to all of the chemical constituents of a medical device presents an acceptable health risk, additional chemical testing is not necessary.

So, you may be able to justify not conducting an E&L study if you have a sufficiently detailed understanding of the materials and manufacturing of the device.

However, we are now seeing an increasing expectation from notified bodies and regulatory authorities around the world, for E&L data for a wide range of device types; not just for long term implants.  It is of course still vital to gather all available information on the chemical composition of the device first, to make sure that IF you do conduct an E&L study, it can then be appropriately designed to address residual risks.  We have seen too many poorly designed E&L studies, which raise more questions than they answer, rather than focussing on key issues of concern.

IMed collaborates regularly with the Chorley Consulting team for client’s needing biocompatibility testing or a safety assessment strategy for their medical device. So, if you need to know more on either of the points above, or any other aspect of evaluating the biological safety of your device, then please contact Philip and his team at

Phil Clay

Phil Clay

Director and Principal Consultant, Chorley Consulting Ltd