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Four Important Things to Know About Particulate Testing and Medical Devices

Particulate testing is required for medical devices to ensure patient safety, but there isn’t a lot of guidance available.  Here are four important things you need to know about particulate testing on medical devices.

First, while there are some device-specific standards, such as ISO 14708-1, -2, -3, -4, -6 for active implantable medical devices, ISO 8536-4 for gravity fed infusion devices or TIR42 for vascular medical devices, there isn’t an overall test standard for medical-device particulate testing.  Particulate analysis is based on analyzing a liquid sample via light obscuration or the microscopic method.  To perform a particulate test, an extraction is required to remove the particulates from the device and put into a solution for analysis.  Although it is specific for injectables, USP <788> Particulate Matter in Injections, is the most commonly used standard for device analysis.

Second, the manner in which the device is extracted can have a significant impact on the reported particulate count.  Careful thought should be taken to ensure the extraction method and extraction volumes are representative of clinical use. The extraction method should be documented so it can be consistently performed between each test.  Steps should also be included to minimize potential contamination during the extraction process.

Third, particulate limits should be set for the device that are meaningful and appropriate.  Setting a limit too high could allow potentially harmful product to be released to market and setting a limit too low could result in failed product that is actually safe to use.  While there are limits in the injectable standard and the product specific standards, those limits may not actually be appropriate for your device.

Fourth, there is no defined sample-size number for particulate testing on medical devices.  USP <788> says, “The number of test specimens must be adequate to provide a statistically sound assessment.”  USP <788> does mention a sample size of 10 units or fewer using an appropriate sampling plan. However, this standard is for production pharmaceuticals that are produced in large homogenous batches and then filled in individual containers.   A sample size of 10 may not be appropriate for medical devices, which are produced individually and subject to more variation in particulate counts.  A sampling-size justification (how many to sample) and sampling plan (when and where to sample) should be developed based on risk, incorporating a statistically significant rationale.

Particulate testing on medical devices can be challenging, due to the lack of a defined test method.  However, keeping these four points in mind, these challenges can be overcome.  The unknown and undefined aspects of particulate testing can be defined, by each manufacturer, using the same principles that are common to other types of tests performed on medical devices.   If this task seems overwhelming, consider partnering with the Expert Advisory Services (EAS) group at Nelson Labs.  Our experts are a great resource and can assist you with creating appropriate extraction methods, selecting and setting particulate limits, and completing sample-size justifications or any other task.