Session 4: Establishing cleaning limits

Sponsored by ASTM Committee F04 on Medical and Surgical Materials and Devices

Establishing and Justifying Limit Values for Residual Analysis

Kierstan Andrascik, QVET Consulting, Layton, UT

There are no established regulatory limits for residual analysis. The primary reason for this is due to the number of variables involved. Every contaminant has differing degrees of toxicity, and that toxicity can change depending on where and how long it is exposed to the patient. Therefore, regulatory agencies have left it up to individual companies to establish and justify residue limits.

Probably the most common technique used to justify residue limits is performing biocompatibility testing. Demonstrating the biocompatibility of the clean devices shows that residues on that clean device are also biocompatible. Cytotoxicity and other biocompatibility tests are performed based on where and how long the device is exposed to the patient.

Other tests that may be beneficial to perform are endotoxin and bioburden. These tests would only be necessary if you wish to claim that the cleaning process reduces endotoxin or bioburden levels.

Another common technique for establishing and justifying residue limits is through comparison. Once all of the data has been collected concerning the residue amounts on the devices, various statistical calculations can be performed to establish residue limits. Clean samples from within a cleaning run can be compared to each other to confirm uniformity in a single cleaning run. Clean samples from multiple cleaning runs can be compared to demonstrate consistency from run to run.

When the cleaning process being validated has been established for a while, there is usually inventory available that was cleaned months or years before. These «off the shelf» devices can be analyzed to establish baseline data and compared to freshly cleaned devices. Since these devices have a history of non-problematic patient use, an appropriate acceptance criteria is that the amount of residue on the freshly clean devices needs to be the same or less than the corresponding «off the shelf» devices.

Another technique is a risk-based assessment which would include data concerning where patient exposure occurs and for how long. The risk of the detected residue amounts may be evaluated using available LD50 data for the target contaminants. Other available toxicity data can also be used (i.e. TDLO). Of course this data may not be readily available due to the proprietary nature of many manufacturing and cleaning materials.

Limits need to justifiable, but it is nice to have some wiggle room. Once a limit is established, it is much easier to justify lowering the limit than it is raising the limit. Regardless of what technique is used, regulatory agencies expect that limit values will be set for residual analysis.

Residual Soil on Reusable Medical Devices: How to Determine Limits?

Steve Goldstein, Steve Goldstein Consultants, Albuquerque, NM

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