Reprocessing is the term we use to describe the cleaning and sterilization of used and dirty, or soiled, medical devices so that they can be used again in the clinic. Cleaning, as the name suggests, is the process of removing from the medical device any contaminants resulting from the clinical use of this device. For all reprocessed medical devices, the device must be sufficiently cleaned before it can go on to sterilization, as any residual contaminants remaining on the medical device can compromise the efficacy of the sterilization process. This will make the device more difficult to effectively sterilize and as well harder to clean after the next clinical use, ultimately posing harm to patients.
When developing a cleaning procedure for a new critical or semi-critical medical device that requires reprocessing, this procedure cannot simply be “wash the device until it looks clean”. Instead, the cleaning procedure needs to be clearly outlined, with variables such as water temperature or amount of detergent be clearly defined, so that the device can be consistently cleaned across different reprocessing technicians and multiple reprocessing sites. Moreover, the developed cleaning procedure needs to be validated with experimental data from scientifically-based cleaning validation studies to show the procedure does effectively remove contaminants from the medical device. In fact, detailed cleaning validation data is part of the submissions that medical device manufacturers would need to send to regulatory agencies like the FDA or Health Canada for device approval.
In a validation study, the medical device would need to be intentionally soiled in a way just like how the device would be soiled in the clinic, followed by carrying out the proposed cleaning procedure, and lastly assessing the effectiveness of cleaning. In the latest version of the standard on the validation of cleaning procedures of medical devices from the American Association of Medical Instrumentation (AAMI), AAMI ST98:2022, it is stated that for a cleaning procedure to be deemed effective, the procedure must remove certain biochemical substances commonly found contaminated medical devices to levels below defined thresholds. These contaminants and their thresholds are:
Protein: ≤ 6.4 μg/cm2
Hemoglobin: ≤ 2.2 μg/cm2
Carbohydrates: ≤ 1.8 μg/cm2
Total organic carbon: ≤ 12 μg/cm2
Total ATP: ≤ 22 fmol/cm2
How would one quantify the amount of these contaminants remaining on a medical device after the cleaning procedure? The first step would be to extract these residuals from the cleaned medical device into a solution to make measurement possible, followed by analysis of the extract solution for these biological contaminants. Here at SteriLabs, we would use one of our many developed procedures to extract residuals on medical devices, such as sonication, agitation, or swabbing, which each have their own advantages depending on the design and specifications of the device. Then, we would measure the levels of the contaminants in the extract solution using our standard biochemistry assays; using residual protein contamination as an example, we would use the Micro BCA assay, a highly-sensitive, microplate-based method for measuring levels of proteins that is suggested by the AAMI standard. In this assay, the absorbance of the solution containing extracts from the medical device is compared to the absorbances of a series of standard solutions with known protein concentrations via what is known as the standard curve. From this, we can get the protein concentration in the device extract solution, and through a series of calculations, we would be able to determine whether the level of residual proteins on the medical device after cleaning would be below the threshold criteria stated in the AAMI standard.
Figure 1. Image of an example microplate used to run MicroBCA assay. At SteriLabs, our biochemistry assays follow the industry standard of a minimum of 3 technical replicates for each sample and standard solution to ensure the accuracy of our results.
Figure 2. Image of an example absorbance vs concentration graph for the standard solution series (Standard Curve) of the Micro BCA assay. The protein concentration of a sample extract solution will be determined by comparing the absorbance of the solution to this standard curve
The shift towards absolute and quantitative assessments to validate the cleaning procedures of medical devices over the years comes as a response to the increasing complexity of medical devices and risks from new pathogens. The need for laboratory analysis in cleaning validation studies can be difficult to meet for medical device manufacturers, as they may not have easy access to the required specialized lab equipment and trained staff. At SteriLabs, our team of experts is happy to assist medical device manufacturers in developing cleaning and complete reprocessing procedures for a new medical device being introduced to the market. Then, we can perform validation of these developed procedures using our state-of-the-art, CALA-accredited, ISO 17025-compliant laboratory. Furthermore, since we are attached to our sister medical device reprocessing facility at SteriPro, we can be your one-stop shop for your needs in medical device reprocessing. Send us an email or give us a call to see how we can help you bring your innovative medical device to the clinic!
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