Biological Evaluation, Risk Assessment and Biological Safety Assessment of Medical Devices
An upcoming revision of ISO 10993-1 will seek to reduce the reliance on in vivo testing with an increased emphasis being placed on data from other sources. On such source is material characterisation as described in ISO 10993-18 Biological evaluation of medical devices -- Part 18: Chemical characterization of materials. Analysis of extractable chemicals can be combined with other information to demonstrate biological safety. Other possible inputs into the risk analysis (and hence safety evaluation) include clinical experience with similar products, safety data on the materials, and previous use of the materials. The material characterisation discussed in ISO 10993-18 includes consideration of surface morphology and chemistry, the geometry of the device and its application. The standard also gives a structured methodology for identifying equivalency between applications.
Once extractable and leachable substances have been identified their associated risk can be assessed through the application of Safety Concern Thresholds. The primary thing to consider is; what is the maximum dose that can be given to a user and over what period. This information along with details such as the target patient population (e.g. what is the minimum mass of patient likely to use the product) and whether use is occasional or chronic, can be used to evaluate if the gain outweighs the risk (whilst bearing in mind ways to mitigate the risk). The PRQI uses the Crammer index to classify risks, whilst employing a 10x overdose factor. This classification can be effected by using Toxtree . A QSAR assessment may also be used to ascertain the risk level posed by a chemical.
The new version of the biocompatibility standard will include a flow chart showing how the information gathered may be used to make a decision about the toxicological safety of a device.
MET’s services include comprehensive materials characterisation of your device along with (if necessary) a toxicological risk analysis.