by Christophe Lambert, editor ZENTRALSTERILISATION
The sterile state is defined as a probability. The person responsible for the sterile state therefore assumes a statistical risk. While it is accepted that achieving a sterility assurance level of 10-6 is a performance requirement, the different methods of doing so do not necessarily have the same destructive power, and thus possibly not the same safety level. In a recent article, Rutala et al. (1) reported a microbicidal activity failure rate of 76% for sterilization processes with vaporized hydrogen peroxide in the presence of sodium and salt crystals. Under the same conditions, the success rate of a steam sterilization process was 100%. This finding will no doubt draw criticism from those who argue that sterilization should only be carried out on a medical device that is perfectly clean. One can only properly sterilize what is clean! Hence, the problem is with the cleaning step, an issue well identified in several articles dealing with this topic, including in this excellent journal!
As regards this fundamental step, the published studies have investigated different analytical methods and techniques. These demonstrate either significant efficacy differences between the commercially available detergents or different levels of residual proteins. Other studies debate the most appropriate methods for detecting these residues and exploring their nature. While each of these studies is undoubtedly interesting and their findings present a challenge to us, several aspects continue to be controversial.
These include the required performance level for washer-disinfectors (WDs) specified by standard EN ISO 15883-5 (3 μg/cm2 residual proteins per instrument) as well as the associated warning level. Are these correlated with an actual clinical risk to the patient or are they a benchmark that can be actually measured today thanks to the sensitivity of the detection methods? When one measures a blood alcohol level it is obvious that this is undeniably correlated with a set of symptoms and clinical consequences which manifest in accordance with the blood alcohol level. This is also true for numerous markers and bioassays. What does this warning value of 6.4 μg/cm2 actually mean for our instruments? Advocates of the 6.4 μg warning value will confidently reply that this is proof of an inadequate automated cleaning process performance! That is correct but it would be a pity to forget too quickly that even incorrect positioning of an instrument within the WD can produce such a result. Indeed, this is observed quite often in my domestic dishwasher and equally often in our Reprocessing Units for Medical Devices (RUMEDs) because of negligence on the part of reprocessing personnel.
However, once overshooting of this well-known 6.4 μg value has been brought to my attention, I intend rectifying it. Am I sure beforehand that the assay method used (OPA, BCA, immunofluorescence, etc.) is really the most suitable? Could there be any possible or probable interference with my detergent? I must add that a value has legitimacy only if it refers to a standard and the method or instrument used has itself been calibrated.
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Is this indeed, apart from all the scientific research activities, the reality of the means and methods applied by us? Fortunately, our sterilizers and, more specifically their measuring instruments, have been calibrated! This is also true for these test soils and their broad diversity which bring only confusion and different interpretations. Let’s be clear there is no soil able to guarantee the reproducibility of the cleaning efficacy and reproduce the complexity of biological fluids, because the composition of these soils resulting from clinical use is changeable and highly variable (proteins, fibrin, mucus, etc.). The article published in this journal issue compares various soil tests for evaluation of the cleaning efficacy. Will this help to shed light on our practices for evaluation of the performances of our washer-disinfectors?
There can be no denying that the sterile state of a specimen is easier to demonstrate and that besides its absence is unquestionably more harmful to our patients. And, if unable to guarantee a cleaning assurance level, our risk analysis did not have to take account of a broader range of elements to assure the quality of the end product. Relying on the conclusions drawn from the article cited in the introduction to this editorial, and with a few ready exceptions (length of channels, materials, etc.), the outcome of a vaporized hydrogen peroxide (vH2O2) sterilization process for a perfectly clean medical device should not be able to fail. Hence, conversely, a medical device that demonstrably presents a cleaning challenge should not be subjected to vH2O2 sterilization. Accordingly, and being apparently unable to assure this cleanliness prerequisite (what level acceptable?), should I not systematically resort to sterilization and packaging levels offering the highest safety level? The answer is obvious and single use still appears to have a bright future.
Implausibly or incongruously, the question of single-use reprocessing is also being addressed in this present issue. Crisis situations and shortages are often the leitmotifs of these practices and serve as open doors for derogatory practices. However, when experts in this field or the healthcare authorities (2) suggest we reprocess items based on methods whose reliability has been criticized, and without having in place a pre-cleaning protocol, my scepticism about the cleaning performance level to be achieved is further reinforced.
(2) RIVM. Reuse of FFP2 mask. Consulted on 20 May 2021: https://www.rivm.nl/en/documenten/ reuse-of-ffp2-masks