Reprocessing of medical devices: Cleaning validation
In the article “Reprocessing of reusable medical devices“, we have already provided a comprehensive overview of the individual reprocessing steps and explained the regulatory framework in more detail. In this article, we will now focus specifically on cleaning as one of the central processes within reprocessing. We will highlight the regulatory requirements and scientific principles of cleaning validation and provide practical advice on how to implement it efficiently and in compliance with standards.
Manual and automatic cleaning
A basic distinction is made between two cleaning methods: manual and automatic cleaning.
Manual cleaning usually involves several consecutive steps, such as immersion in a cleaning fluid, mechanical brushing and subsequent rinsing. Automatic cleaning, on the other hand, takes place in a washer-disinfector (WD) and may include manual pre-cleaning to remove coarse contaminants in advance.
According to EN ISO 17664-1:2021 (sections 6.6.1.1 and 6.6.1.2), the following applies from a regulatory perspective:
“At least one validated machine cleaning procedure – which may include validated manual pre-cleaning – must be established, unless the medical device is not suitable for such a procedure. In this case, the user must be informed accordingly. If machine cleaning is not possible, a validated procedure for manual cleaning must be established.”
Regardless of the method chosen, detailed, step-by-step working instructions must be drawn up and made available to the user as part of the reprocessing instructions.
For automatic cleaning, it must also be taken into account whether the medical device is cleaned in specific baskets or adapter systems. These must be taken into account in the cleaning validation and, if necessary, evaluated separately, as they can influence the cleaning and rinsing results.
Regulatory background
Before we turn to the details of cleaning validation, here is a brief overview of the most important standards:
- ISO 17664-1: 2021 Processing of health care products – Information to be provided by the medical device manufacturer for the reprocessing of medical devices – Part 1: Critical and semi-critical medical devices
- ISO 17664-2: 2021: Processing of health care products – Information to be provided by the medical device manufacturer for the reprocessing of medical devices – Part 2: Non-critical medical devices
- Hygiene requirements for the reprocessing of medical devices
Recommendation of the German Commission for Hospital Hygiene and Infection Prevention at the Robert Koch Institute (RKI) and the Federal Institute for Drugs and Medical Devices (BfArM): 2012 - AAMI TIR12: 2020 (R2023) Designing, testing, and labeling medical devices intended for processing by health care personnel: A guide for device manufacturers
- ANSI/AAMI ST98: 2022 Cleaning validation of health care products—Requirements for development and validation of a cleaning process for medical devices
- Reprocessing Medical Devices in Health Care Settings: Validation Methods and Labelling. Guidance for Industry and Food and Drug Administration Staff 17 March 2015
Determination of test contamination
Before starting the cleaning validation of a medical device, a few basic conditions must first be defined. These include, to name just a few examples, defining the worst-case device in the case of product families, determining the target markets, determining the service life (e.g. how many reprocessing cycles the product can undergo), selecting the cleaning agents to be used, and providing a detailed description of the clinical application.
Once these fundamental points have been defined, the actual work of cleaning validation can begin. The starting point should always be the clinical application of the medical device. It is advisable to analyse the exact clinical procedure in detail in order to clearly understand the intended purpose of the product.
This information forms the basis for determining a suitable test soil. ASTM F3208-20 describes procedures for selecting and composing potential test soils, while ISO 15883-5 also provides valuable guidance on their selection and application.
However, simply selecting a test soil is not enough. It is crucial that the selected soil simulates clinical reality as accurately as possible. This means that the type, quantity and composition of the soil must correspond to actual clinical residues in order to enable a valid and reproducible evaluation of the cleaning performance. Only if this simulation adequately reflects the actual use of the medical device, the validation can be considered scientifically sound and regulatory acceptable.
Simulated use
In cleaning validation, it is essential that the medical device is not only treated with a suitable test soil, but also under the correct conditions of use. It is crucial that the clinical application procedure is simulated as realistically as possible – a concept known as simulated use.
Simulated use must take into account the actual conditions of use, especially those that represent the worst-case clinical application. These include, for example, drying times that can promote the adhesion of residues to the product, as well as chemicals, lubricants or other substances used in maintenance.
The aim of simulated use within cleaning validation is to deliberately provoke the accumulation of test contamination in order to ensure realistic stress on the medical device. A complete application and reprocessing cycle should be taken into account – including contamination, handling, drying, cleaning and subsequent steps such as disinfection and/or sterilisation.
Usually, six simulated use cycles are performed before the actual validation of the cleaning performance takes place in the seventh cycle. This procedure ensures that the evaluation is carried out under conditions that are reproducible and close to worst-case scenarios – a crucial aspect for the scientific traceability and regulatory acceptance of cleaning validation.
Validation
After the medical device has been subjected to appropriate stress in the previous simulated use cycles, the actual extraction takes place in the seventh cycle. In this step, the product is, for example, immersed, rinsed or wiped to remove and extract any dirt and residue from the surface.
A key aspect in this context is the determination and verification of recovery efficiency. This serves to prove that the selected extraction method is capable of reliably detecting the relevant analytes within a defined range of values.
To ensure the validity of the procedure, both positive and negative product controls are used. These enable reference values to be defined and serve to verify the measurement results within the validation.
While the standard parameters (temperature, concentration, exposure time) are used in simulated use, it is essential to select the worst-case conditions within the validation cycle. This means that the parameters are set at the lower limit of the specifications for the specified cleaners in order to evaluate cleaning under difficult conditions.
In addition, the seventh cycle exclusively comprises the steps of soiling, drying and cleaning – processes such as disinfection or sterilisation are deliberately not taken into account at this stage in order to evaluate the pure cleaning performance in isolation.
For critical and semi-critical medical devices (according to the Spaulding classification), both a visual inspection and analytical testing of at least two clinically relevant analytes are required. In this context, ANSI/AAMI ST98 provides specific acceptance criteria for various analytes and thus represents an important normative basis for evaluating cleaning efficiency.
Once these tests have been successfully completed, the cleaning efficiency is considered proven – but that is not the end of the process. Following cleaning validation, it must also be checked whether any chemical residues from cleaning or process chemicals remain on the product. Only this additional assessment provides complete proof of the overall safety of the medical device with regard to reprocessing.
Rinsing Validation
The evaluation of chemical residues on medical devices is an essential part of cleaning validation. There are two main reasons for this: Firstly, residues from process chemicals can have a negative impact on subsequent reprocessing steps and impair their effectiveness. Secondly, it must be checked whether any remaining residues pose a potential risk to patients, users or third parties.
The choice of a suitable detection method for process chemicals depends directly on the cleaning agents used. In the case of toxic cleaning agents, rinsing validation may include a cytotoxicity assessment in accordance with ISO 10993-5 in order to identify possible biological risks. In the case of non-toxic cleaning agents, however, the residual concentration of the cleaner can be determined using alternative analytical methods – such as protein analysis or other specific analyses tailored to the chemical composition of the respective cleaner.
In contrast to actual cleaning validation, rinsing validation uses the maximum process parameters (temperature, concentration, time). This is intended to deliberately create a worst-case scenario that promotes the accumulation of process chemicals and thus enables a realistic assessment of the possible residue risk.
Outlook
Although the primary purpose of cleaning validation is to demonstrate that a defined procedure reliably achieves the required cleaning performance, the overarching goal must not be forgotten: patient safety. Passing validation alone is insufficient if the procedure is too complex or too costly to be consistently implemented in clinical practice.
Therefore, the principle should be: as simple as possible, as robust as necessary. Reprocessing procedures must be based on the real conditions in the hospital and take into account that users do not always have the capacity to read complex instructions in full and implement them correctly.
A decisive factor for patient safety lies in the product design. Products should be designed according to the concept of “design for cleanability” so that they are easy to clean and require as few manual intermediate steps as possible. Such an approach not only reduces the risk of human error, but also facilitates the validation of cleaning and disinfection procedures and supports compliance with regulatory requirements as specified in the MDR and ISO 17664.
In the next blog article, we will focus on disinfection – the key step after cleaning. We will show how validated disinfection procedures, combined with a well-thought-out cleaning design, can ensure the microbiological safety and regulatory compliance of medical devices.
So stay tuned or contact us directly if we can also support you in developing your reprocessing instructions.
