Protein residuals on reusable medical devices and patient safety impact

Authors: T.A. Kremer*, A. Patel, C. Summers, M. Quin, K. Lemons, G. McDonnell 


Cleaning is an essential step to ensure the safe processing of reusable medical devices. In recent years, national and international standards and guidelines have matured to define scientifically sound analytical requirements to define endpoints for cleaning.  Although these requirements can be based on what is practically achievable in clinical practice, it is important to ensure that cleaning endpoints are scientifically based to ensure patient safety. The impact of protein cleaning endpoint concentrations at or greater than 6.4 µg/cm2, the current recommended cleaning level, in posing a toxicity or immune risk to patients has not previously been evaluated. This study investigated the impact of residual protein levels on patient toxicity and concluded that an acceptable level of protein in cleaning efficacy studies to be in the 3-6.4 µg/cm2 range.


Reusable device processing can be defined as activities to prepare a new or used device for its intended use.  Processing steps can include cleaning, disinfection, and/or sterilization, depending on the device criticality. The types and levels of residual clinical soil (e.g., blood, tissue, bone, mucus) found on these devices following patient procedures can vary considerably depending on their clinical and surgical use (Table 1).  To better characterize the challenge for reprocessing these devices an assessment of the biochemical levels on devices was first studied in detail by Alfa et al (2), which focused on flexible endoscopes before and after detailed manual cleaning of the instrument suction channels of various endoscopes.  This, and other similar studies (1, 3) have subsequently guided those interested in validating methods for processing reusable medical devices to choose protein as the most common biochemical marker, and the residual protein level acceptance criteria has been established in certain standards and guidance documents to be <6.4 µg/cm2 regardless of clinical use (2, 4). However, in some cases, more stringent levels of protein have been recommended based on practical experience in clinical practice (≤100 µg/device, depending on the device side; 5, 6) or based on reducing the risk of prion contamination (5 µg BSA equivalent per instrument side; 7).  


  • protein
  • cytotoxicity
  • residuals
  • cleaning
  • reusable device
  • endpoints
  • tests
  • acceptance criteria   
  • toxicity

Although such requirements are useful, they should consider overall patient safety. Residual protein remaining on a device before patient use presents several patient safety concerns. First, residual protein buildup may prevent the effectiveness of the disinfection or sterilization process. Second, the patient may experience an adverse immune response to residual protein. A further consideration is the risk of prion contamination and transmission potential on surgical devices, but this may not be assumed to be achieved by focusing on detectable protein reduction alone (8).  

Studies have shown that various chemical and physical methods used for the disinfection or sterilization processing of reusable medical devices are effective even under visual soil conditions, so the first safety concern for residual protein has been well characterized.  For example, disinfectants and sterilization processes are often tested in the presence of visual soil in accordance with various standards, such as 5-10% serum or BSA (9) or 3g/L BSA + red blood cells (10). In both cases, these levels of visual soil would be greater than ~50 µg/cm2 (the approximate visual detection level of protein on device surfaces).  It is, however, important to note that disinfection or sterilization cannot be assumed to be achieved on devices with visual clinically soiled surfaces and soil build up in certain areas of devices can lead to ineffective penetration of these antimicrobial [...]

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Kremer T.A., Patel A.,  Summers C., Quin M., Lemons K., McDonnell G.
Protein residuals on reusable medical devices and patient safety impact.
Zentr Steril 2019; 27 (3): 178–183


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