"Reprocessing validation" – definition, procedures, and tests according to DIN EN ISO 17664 and DIN EN ISO 17665

• EU Medical Device Regulation (MDR 2017/745): Manufacturers must provide detailed reprocessing instructions for reusable medical devices and validate their effectiveness.

• DIN EN ISO 17664-1/-2: Specifies what information the manufacturer must provide for reprocessing (cleaning, disinfection, sterilization, drying, inspection, packaging, storage).

• DIN EN ISO 17665: Specifies the requirements for the development, validation, and control of the application of a steam sterilization process for medical devices.

• Medical Devices Operator Ordinance (in Germany: MPBetreibV, §8): Reprocessing must be carried out using suitable, validated procedures to ensure the safety of patients, users, and third parties. Proper reprocessing is assumed if the KRINKO-BfArM (German institution) recommendations are followed.

• Infection prevention: Validated procedures minimize the risk of nosocomial infections, which cause thousands of deaths every year.

• Safety and functionality: Validation ensures that the medical device is free of microbial contamination after repeated reprocessing and retains its function.

• Transparency and traceability: Documented validation creates trust and legal certainty for users and patients.

• Normative basis: DIN EN ISO 14971 (Risk management for medical devices).
• Objectives of risk assessment:
  • Identification of typical contaminants (e.g., blood, proteins, biofilm).
  • Selection of suitable methods (manual, mechanical, chemical, thermal).
  • Definition of acceptance criteria (e.g., residual protein < 6.4 µg/cm², bioburden reduction).
• Manufacturer's obligations:
  • Provision of validated reprocessing instructions.
  • Performing worst-case analyses (e.g., hard-to-reach areas, maximum contamination).
  • Documentation and proof of effectiveness.

The validation of reprocessing procedures must be carried out under conditions that simulate clinical use as realistically as possible. This applies both to the type of contamination and to the test methods used to verify the effectiveness of cleaning and disinfection.

Simulation of real contamination

The biggest challenge is to replicate the typical contaminants after the medical device has been used as intended. This simulation must take the following aspects into account:

• Type of contamination: Blood, tissue, proteins, fats, biofilm, possibly microbiological contamination (depending on the clinical application).
• Worst-case scenarios: Narrow passages, complex geometries, surfaces that are difficult to access, possibly also materials.
• Drying time: In practice, contaminants often dry, which makes cleaning more difficult. 

Example of a realistic simulation:

• Use of sheep blood or synthetic test contamination (e.g., Browne Soil) to simulate blood and protein residues.
• Application to critical areas of the product (e.g., joints, lumens) in accordance with expected real-life contamination (or a worst-case scenario thereof).
• Allow to dry for e.g., 2 hours at room temperature to simulate clinical reality.
• Finally: Perform the cleaning and disinfection procedure specified by the manufacturer. 

Typical test methods and objectives

The laboratory tests serve to verify the effectiveness of the treatment. They can be divided into three main categories:

a) Chemical testing methods

• Protein residues:
  • BCA test (bicinchoninic acid): Quantification of residual protein in µg.
  • TOC analysis (Total Organic Carbon): Detection of organic residues (including cleaning agent residues).  
• Objective: To verify that cleaning removes organic contamination and remains below limit values (e.g., < 6.4 µg protein per cm² of medical device surface). 

b) Microbiological testing methods

• Bioburden test: Determination of the bacterial count before and after cleaning (ISO 11737-1). Country-specific requirements for bacterial count reduction must be met.
• Sterility testing (during sterilization validation): Testing for sterility
• Objective: To ensure that disinfection and sterilization are effective. 

b) Material and functional testing (by the manufacturer)

• Mechanical tests: Testing joints and closing mechanisms after repeated cleaning.
• Objective: To ensure that the product retains its function and integrity. 

acceptance criteria:

• Residual protein below threshold value.
• Microbiological reduction to defined level.
• No material damage.

Measures in case of non-compliance:

• Adjustment of processing instructions.
• Selection of alternative processes or chemicals.
• Limitation of the product's service life.

Documentation:

• Validation report as proof for authorities and users.
• Revalidation in the event of changes to the product or process.

The validation of reprocessing procedures is a legally required and safety-related process. It protects patients from infections, ensures the functionality of medical devices, and meets regulatory requirements. Manufacturers are responsible for demonstrating the effectiveness of their instructions through risk assessment and laboratory testing.