Reading recent literature1, there appears to be a growing momentum that proteins may cause more than variant Creutzfeldt-Jacob disease (vCJD). The attention is now focusing on causes of Alzheimer’s disease and this raises new questions surrounding effective decontamination of surgical instruments or identifies new equipment that should be considered for a switch to single-use.
Prion Proteins and vCJD
The 1980’s and 1990’s brought to public awareness, mad cow disease or bovine spongiform encephalopathy (BSE). This has resulted in the probable deaths from new vCJD of 178 patients according to the NCJDRSU (National CJD Research & Surveillance Unit).
During this period, recognition of the need for more effective cleaning and sterilisation was heightened. Consequently this produced an impetus for more sterile single-use instrumentation especially equipment that was the most difficult to re-process. Occluded instruments like the Negus Aspirating Dissector and Spackman Insufflation Cannula, and angled narrow lumen suction handles like Fraziers, Microlaryngeal or Barrons were soon changed for sterile single-use alternatives.
With the advent of NICE guidelines in 2008 the situation for Neurosurgery and Posterior Ophthalmic Surgery was clarified and single-use should only be used in view of the risk from vCJD. This is still the case today.
Effective prion protein cleaning and decontamination remains unresolved practically for routine use in most sterile services units. Single-use instruments, like Neuro Burr trays, are used for patients with the highest risk of CJD to avoid quarantining expensive reusable equipment.
Protein Misfolding Diseases?
Prions are probably the best know example of “protein misfolding disease” and this term is becoming more common. The first question is; Are they be transmissible? This is quickly followed by How do we prevent or minimise this?
Considerable research is looking at the causes of cell death and tissue loss as a result of protein misfolding; in Parkinson’s caused by a new type of prion, and iatrogenic CJD, due to contamination from an infected person as a result of a medical procedure.
In view of the high incidence rates (1.5 per 100) the work in Alzheimer’s may become the most vital of all because of the impact it has on so many individuals and their families.
According to the Alzheimer’s Association, the prime suspects of nerve cell death are beta-amyloid plaques. Plaques form when protein pieces of beta-amyloid that originate from a larger protein found in the fatty nerve cell membrane, clump together. These plaques are sticky and build up gradually and this may block nerve cell to cell signalling and other effects to produce the recognisable symptoms of Alzheimer’s.
It is likely that these and other protein misfolding diseases will receive more attention from researchers and will generate headlines, possibly shocking in the next few years as our knowledge grows.
The Challenge for Reprocessing
Cleaning and decontamination of prions, and probably other proteins connected with protein-misfolding like beta-amyloids has still to be resolved for widespread satisfactory use.
Equipment like the ProReveal system identify very clearly how difficult it can be to remove proteins from surgical instruments. It is also recognised that proteins adhere strongly to stainless steel and plastics. This is presenting new challenges for decontamination and sterile services units where more regular testing is encouraged.
Updated Guidance2 from the ACDP TSE (Advisory Committee on Dangerous Pathogens, Transmissible Spongiform Encephalopathy) Subgroup on prevention of CJD and vCJD now includes a section on “Protein Detection” as part of the post cleaning and disinfection inspection of re-usable instruments. They also set an upper limit of 5 µg BSA (Bovine Serum Albumin) equivalent/instrument side for regular protein challenge tests.
With recent research identifying more risk from protein folding diseases it is likely these tests will become more important resulting in more attention on effective processes for decontamination.
Wet is Best
The recent ACDP TSE guidance recognises “that allowing surgical instruments to dry for more than fifteen minutes before reprocessing greatly increases the amount of residual protein contamination.”
Immediate reprocessing is advised and practically this may lead to sterile services procedures that are closer to just in time.
If this is not practical, the guidance proposes instruments are kept moist which could lead to more bathing in enzyme cleaners like Klerzyme before or during transportation. This may demand more attention on health and safety of staff to ensure spillage or other risks are avoided.
All of these challenges will have an impact in the future and give rise to new considerations about the best methods to employ. In clinical settings remote from sterile services like community and private hospitals and outpatients clinics this will present particular difficulties.
Whilst reprocessing represents the best solution in many cases, it is likely that a combination of factors will lead to more single-use instrumentation. More effective decontamination may be impossible to reach exposing a wider patient population to cross contamination as research and practical experience increases.
Fortunately, if this scenario turns into reality, the sterile single-use supply chain is well established and most instruments that are likely to be needed can be provided readily to meet the impetus for new demand. However this may set manufacturers like DTR Medical additional challenges to effectively supply high quality products with the required reliable service level healthcare providers will need.
Impetus for Innovation?
Currently much of the demand for single-use is met from far East low cost manufacturing. This is heavily dependent on a skilled workforce capable of producing instruments of a consistent quality in volume. If these new challenges increase the demand it is feasible the quality and service will not be able to keep up.
If research into protein folding disease continues to reveal risks of transmissibility then this work will drive medical device manufacturers to innovate new materials, processes, and designs that can cope with the extra volumes of single-use surgical instruments that may be needed.
DTR Medical recognises the importance of innovation to respond to customer needs and we have a full programme of product and process development aimed at meeting these challenges.
We welcome thoughts and advice that will help us meet any new impetus we will be required to respond to.
1 Tackling the Problem of Prion Proteins, Clinical Services Journal May 2016
2 Transmissible Spongiform Encephalopathy Agents: Safe Working and the Prevention of Infection: Annex C