The public often thinks of medical devices as complicated constructs of metal, plastics and electronics, but the fact is that many medical devices are made from animal-derived materials as well.
Some constitute large parts of the device, such as a bone substitute or bovine heart valve; others are smaller portions, such as a heparin coating on a device.
But as a new guidance from the US Food and Drug Administration (FDA) notes, whatever portion of the device is made from animal-derived parts, it runs the risk of being contaminated with microorganisms.
FDA's latest guidance, Medical Devices Containing Materials Derived From Animal Sources (Except for In Vitro Diagnostic Devices), is meant to replace an earlier 1998 guidance and address newly recognized risks, such as those from all strains of transmissible spongiform encephalopathy (TSE).
The 1998 guidance had focused largely on the risk of bovine spongiform encephalopathy (BSE), better known as mad cow disease, but lacked reference to a number of other forms of TSE like scrapie (found in sheep), chronic wasting disease (found in deer) and Creutzfeldt-Jakob Disease (CJD) (found in humans).
Complicating matters is that there are currently no treatments for TSE diseases, and no way of screening for the disease in a live person or animal. The prion-based diseases are also extremely resistant to disinfection and sterilization-a distinct problem for reusable medical devices that come into contact with blood or tissue.
FDA said that it recommended device manufacturers adopt an approach based on vigilance, documentation and monitoring for assessment of TSE risks in their animal-derived devices. Companies using animal-sourced parts in their devices should document (in any regulatory submission) the:
- animal species
- specific tissue used (if multiple tissues are used, identify all tissues used)
- animal's country of origin and country of residence (or a more specific geographic information when appropriate)
- methods for actively monitoring the health of herd and the health of specific animals from which tissues are collected
- information concerning the long-term health of the herd (e.g., documented breeding history, animal traceability, absence of TSE disease, and standard vaccinations such as live modified viruses which could co-purify in the desired tissue) the frequency and type of veterinarian inspections
- animal feed composition (e.g., animal feed history records, including recordation of co-mingling of feeds, and, labeling of animal feed composition at distribution locations) (In 2008, FDA issued a rule prohibiting certain material from being fed to ruminants. The rule may be found at http://www.gpo.gov/fdsys/pkg/FR-2008-04-25/html/08-1180.htm.)
- USDA status of the abattoir
- animal age at sacrifice
- animal sacrifice methods that reduce the risk of cross contaminating non-TSE tissues with material from tissues that could contain TSE
- specifics of the pre and/or post mortem inspections (e.g., gross visual inspection, specific organs and anomalies exams, lab tests such as PrP testing)
- tests performed (and release criteria) for permitting tissue to be further processed and/or combined with other tissues and device components (e.g., a Certificate of Analysis)
This information should be maintained on a lot level, FDA said. Companies should also conduct analyses of how their animal parts are sourced, as a non-TSE-transmitting animal may be slaughtered in a facility that also processes TSE-transmitting animals, such as cattle.
For now, then, FDA says industry should remain vigilant about future evidence. At some point in the future, FDA "may issue rules specifically on BSE and the regulation of medical devices," which would take precedence over the current guidance.
"When a TSE-screening assay is validated to accurately identify TSE-contaminated tissues, FDA will consider revising this guidance as appropriate and recommending that such a test be introduced into the standard operating procedures for bovine tissue collection and processing," FDA concluded.
More general contamination control issues require a more streamlined assessment process, also explained in the guidance. Sterilization processes will also need to be assessed on a case-by-case basis, as will virus validation studies.
Medical Devices Containing Materials Derived From Animal Sources (Except for In Vitro Diagnostic Devices)