Evaluating risk in decontamination

The Department of Health is adopting a change of strategy on decontamination, according to Peter Hoffman, a consultant clinical scientist at the Health Protection Agency’s Laboratory of Healthcare Associated Infection. At the recent Infection Prevention Society’s annual conference in Harrogate, he examined some of the key issues raised by new guidance. He pointed out that people have very different definitions of what the term “decontamination” actually means. The dictionary definition, in essence, describes it as the “removal of infection”, which could be exemplified by the eradication of anthrax from a Scottish island, for example. An alternative definition is “the combination of processes including cleaning, disinfection and sterilisation used to render an item safe” but this is a value-loaded statement, he pointed out. “It is easy to identify what is definitely ‘unsafe’ or definitely ‘safe’, but in between there is a significant grey area – which is dependent on the organism, the type of instrument and the immune status of the patient,” he commented. He pointed out that the present concept of decontamination is driven by the occurrence of variant Creutzfeldt- Jakob disease (vCJD) whose causative agent (a prion) is so stable that normal steam sterilsation does not inactivate it completely. He explained that proteins are constituted from amino acids and the way these are joined together gives the proteins their shape. Prions can change their shape and create a cascade effect or “infectious geometry” in other proteins, which causes those proteins to lose their function – resulting in the symptoms associated with vCJD. “You cannot completely inactivate prions even through six sequential sterilisation cycles. Therefore, there are two approaches to safety,” he explained. “High-risk patients and high-risk tissues within these patients are identified to ensure that any surgical instruments which could be contaminated with prions are treated as single use. Alternatively, in lower risk tissues, where there are a smaller number of prions, the approach may be to remove as many prions as possible, first by cleaning, then by steam sterilisation.” Prion proteins are unusually “sticky” and are “hydrophobic”, he continued, and will “sit on surfaces” rather than float in water – making them very difficult to wash off. This has led to guidance stating that as much organic debris as possible should be removed from instruments before steam sterilisation. This gives rise to a third definition: “Decontamination is conformity with decontamination guidance”. Outlining the background to the guidance, he explained that the first decontamination survey found that staff were not well trained and this was especially evident the further away they worked from specialist areas such as sterile services departments. The situation was very poor, with a lack of satisfactory resources, equipment and dedicated facilities. There were no protocols in place and people were unsure of the procedures they should be following. Equipment also tended only to receive mechanical attention when it broke down. “A lot has changed since those early days. There is now a legislative basis for decontamination – the 2006 and 2008 Health Acts, which require effective arrangements for decontamination to be in place,” he commented.

Health Technical Memoranda

The guidance referred to in these codes of practice are included in the Health Technical Memoranda (HTM). “HTM 01 01: Decontamination of reusable medical devices” Part A, which is concerned with management and the environment, has already been published. Parts B, C and D are in late draft, while Part E is not yet underway. HTM 01 04, which is also relevant for those responsible for infection prevention and control, refers to laundries and is currently in production, while HTM 01 05, which relates to dental services, has now been published. Other HTM versions in the series are also at various stages of development. The core to safeguarding effective procedures is the decontamination lead who is required to ensure that decontamination takes place in appropriate facilities, that the right decontamination equipment is purchased and maintained, the people that operate it know what they are doing, and there is a quality assurance system in place.