Minimising risk of iatrogenic CJD

Last year, the media reported that 21 patients in Essex and 38 in Wales were informed they had been put at risk of contracting Creutzfeldt-Jakob Disease (CJD) as a result of undergoing surgery.1 Although advised that the risk was ‘small’, the patients involved in these incidents spoke of the stress they faced at not knowing whether or not they would go on to develop the degenerative disease, in years to come. These patient stories provide a stark reminder of the importance of minimising the risk of iatrogenic CJD. In the case of CJD, abnormal prion protein can cause normal prion protein to change shape and become abnormal. This leads to a chain reaction which, in turn leads to damage to the brain cells. If decontamination is inadequate, infectious prion protein from one patient can be transmitted to another via contaminated surgical instruments – potentially leading to iatrogenic CJD. While reports suggest the number of variant CJD (vCJD) cases has peaked, there are fears that this may be an initial wave of the disease and there may be further ‘waves’ to come. The problem of CJD has not gone away, therefore, and hospitals need to remain vigilant. At the recent annual conference of the Institute of Decontamination Sciences (IDSc), the challenges hospitals face in tackling this threat were high on the agenda. Professor Bill Keevil, head of the microbiology group and director of the Environmental Healthcare Unit, University of Southampton, gave an insight into the latest research into CJD and scientific approaches to ensuring effective decontamination of surgical instruments. He highlighted the significant challenges that sterile services departments (SSDs) face in eliminating the risk of patient-to-patient transmission, pointing out that the prion agent that is responsible for CJD is ‘an incredibly tough infectious agent’. Prions are extremely resistant to heat disinfection and therefore present a major challenge when sterilising instruments. Furthermore, commonly used testing methods are inadequate, he warned, which means there is a potential risk that instruments may be carrying CJD through the cleaning cycle.

The scale of the problem

In the UK, the numbers of people with reported CJD and vCJD are small, but the concern is that, due to the long incubation period, it could be 25 years or longer before actual manifestation of the disease. In the case of Kuru, in New Guinea, symptoms associated with the transmissible spongiform encephalopathy did not appear for up to 40 years or more after the initial infection in some cases. There are currently 176 reported cases of vCJD in the UK. However, the latest anonymous survey of appendix samples, suggests that a median of around 290 cases per million may be carrying vCJD – this equates to around 18,000 carriers in the UK. The risk of transmission from patient to patient through contaminated medical devices remains ever present, therefore. Cases have been linked to the use of contaminated neurosurgical instruments and sterotactic EEG depth electrodes.2 However, transmission has also occurred with corneal transplants, grafts of dura mater and treatment with human growth hormone. There is also a potential risk from blood transfusion – five cases of transmission through this route have been documented, Prof. Keevil reported. He added that, given the number of people who are unaware that they are carriers of the vCJD molecule, this is a particular concern. “Research shows that SSDs are doing a very good job at decontamination, but the problem faced by hospitals is the fact that they have very quick turnaround times for instruments,” Prof. Keevil commented. “In England, there are around 6.5 million operations per year. It is estimated that there is a turnaround of some 9 million surgical trays, containing over 110 million instruments that require decontamination. “The average sterile services department is handling around 1,500 instruments per day; the turnaround is very short and there is intense pressure to get instruments cleaned and back to theatre, ready for the next patient... Instruments may be in contact with the cleaning chemistry for just five minutes,” he continued.