Test Soil and Material Affinity for Reusable Device Cleaning Validations

While selecting the test variables for a cleaning validation for reusable medical devices, the manufacturer must provide a simulative and clinically representative challenge for the device. An appropriate challenge must be identified with care so as not to overchallenge the cleaning process by selecting the worst case for every variable, thus leading to an impossible validation or unrealistic processing requirements. To appropriately select the testing variables, an understanding of the challenge to the cleaning process is important. The relationship among device material, test soil, and application method was investigated by testing 140 variable combinations, including seven materials (stainless steel, polyoxymethylene, polyether ether ketone, nitinol, aluminum, titanium, and silicone), four test soils (defibrinated blood soil, coagulated blood, modified coagulated blood, and Miles soil), and five soil application methods (pipetting neat, pipetting spreader, painting, handling with soiled gloves, and immersion). Stainless steel was the only material that showed consistent soil application in a thickness (at ~6 μL/cm²) that fully covered the test surface without some element of pooling, cracking, flaking, or soil migration with all test soils and application methods. The data collected using solubility testing indicated that a complex relationship for material adherence may exist between device materials and test soil. Stainless steel was the most challenging material tested.