2 Background

2.1 Remit

The Chief Medical Officer for England asked the National Institute for Health and Clinical Excellence (NICE or 'the Institute'), on behalf of all UK Chief Medical Officers, to develop and publish guidance for the NHS on how best to manage the risk of transmission of CJD and vCJD via interventional procedures.

2.2 Interventional procedures and patient population considered

This guidance covers management of all patients undergoing procedures involving instruments and endoscopes that might pose a risk of transmission of CJD. These procedures have been classified as follows based on the risk of transmission of CJD.

High-risk procedures: Procedures that involve handling of tissue considered to be at high risk of transmission of CJD. High-risk procedures are intradural neurosurgical operations on the brain (excluding operations on the spine and peripheral nerves), neuroendoscopy and posterior eye procedures that involve the retina or optic nerve (see appendix C of the full guidance).

  • Medium-risk procedures: All procedures on tonsils, spleen, lymphoid tissue, spinal cord, anterior eye and peripheral nerves.

  • Low-risk procedures: All procedures other than the high- and medium-risk procedures.

This guidance focuses on the general population. It does not consider the following groups of patients.

  • Symptomatic patients with definite, probable or possible CJD.

  • Symptomatic patients with neurological disease of unknown aetiology where the diagnosis of CJD is being actively considered.

  • Asymptomatic patients at risk of having familial forms of CJD or who have had previous iatrogenic exposure.

For the excluded patient population above, the guidelines set out by the ACDP TSE Working Group and published on the Department of Health website should be followed (see appendix B).

2.3 Clinical and decontamination practice

The following areas of clinical and decontamination practice were considered in terms of clinical and cost effectiveness, patient safety and the extent to which they reduce the risk of CJD transmission.

  • Use of reusable and single-use instruments in surgical procedures.

  • Use of reusable and single-use endoscopes, laryngoscopes and related accessories.

  • Arrangements for cleaning, sterilisation and tracking of reusable surgical instruments and endoscopes[2].

The following areas were not considered in this guidance.

  • Transfusion of blood or blood products, including occupational exposure to blood or body fluids. Several organisations (including the Department of Health Advisory Committee on the Microbiological Safety of Blood, Tissues and Organs for Transplantation, the Spongiform Encephalopathy Advisory Committee (SEAC), the ACDP TSE Working Group and the CJD Incidents Panel – see appendix B) already advise on measures to reduce the risks from blood transfusion, including exposure to blood in the workplace.

  • Extracorporeal life-support machinery, including cardiopulmonary bypass, haemodialysis and ventilator equipment.

  • The risk of CJD and vCJD transmission via drugs and other materials of human or bovine origin. This area is already subject to regulation by the Medicines and Healthcare products Regulatory Agency (MHRA).

  • The safety of transplant grafts. This area is the responsibility of the Department of Health Advisory Committee on the Microbiological Safety of Blood, Tissues and Organs for Transplantation.

  • The decontamination and reuse of single-use instruments. The MHRA has issued guidance against the reuse of such items (MHRA Bulletin DB 2000[04]).

  • General dentistry. The initial remit excluded dentistry, but the Committee nevertheless considered issues relating to dental procedures. After deliberation it was agreed that general dentistry should be excluded. Aspects of dentistry, such as decontamination practices and dental tissue infectivity, are currently being considered by the Department of Health and the Health Protection Agency. Maxillofacial surgery was included in the guidance under medium- or low-risk procedures.

2.4 Context

2.4.1 Types of CJD

CJD is a progressive, fatal neurological disease that belongs to a wider group of neurodegenerative disorders known as transmissible spongiform encephalopathies (TSEs) or prion diseases. TSEs affect humans and animals. Traditionally, there are three aetiological categories of CJD.

  • Sporadic CJD (85–90% of cases) is of unknown aetiology. Sporadic CJD has a worldwide distribution, with a relatively uniform annual incidence of about 1 in 1 million people.

  • Inherited CJD (10–15% of cases) is associated with coding mutations, insertions or deletions in the prion protein gene.

  • Iatrogenic CJD (less than 1% of cases) arises from accidental exposure to human prions through surgical or medical procedures.

CJD patients typically present with rapidly progressive dementia, usually accompanied by myoclonus and cerebellar ataxia. Most patients die within 4 months of disease onset, in a mute and immobile state.

2.4.2 Variant CJD

A novel form of human prion disease, vCJD, was first recognised in the UK in 1996 and is believed to result from consumption of food derived from cattle infected with BSE. Like BSE, vCJD is a fatal neurodegenerative disease that causes sponge-like changes in the brain. vCJD is characterised by extensive lymphoreticular tissue involvement and a young age at onset of disease (the mean age at death is 28 years, compared with 66 years for sporadic CJD). The clinical course of vCJD is also distinct from that of sporadic CJD. Patients with vCJD frequently present with sensory and psychiatric symptoms that are uncommon in patients with sporadic CJD. They then develop progressive neurological signs, such as gait disturbance, ataxia and tremor. The median duration of illness is longer than that for sporadic CJD (14 months compared with 4 months). Death in an immobile and mute state is a typical outcome.

By the beginning of September 2006, 156 people in the UK had died from definite or probable vCJD, and a further six were alive with the diagnosis.

Note that throughout this guidance the abbreviation CJD is used to refer to both sporadic and vCJD (see the glossary, appendix F) unless otherwise specified.

2.4.3 Prions

The prion protein is a normal cellular protein that is widely expressed in almost all human tissues, with the highest levels seen in nerve cells. Prions are infectious particles composed of abnormally folded forms of the prion protein that are thought to cause TSEs, including CJD. They resist complete inactivation by conventional hospital decontamination techniques. Individuals undergoing surgery may therefore be infected by prion-contaminated instruments previously used on patients with CJD.

2.4.4 Iatrogenictransmission

There have been seven cases of iatrogenic transmission of (presumed sporadic) CJD via contaminated neurosurgical instruments or intracerebral electrodes. Five cases resulted from neurosurgical instruments: four in the UK and one in France. All of the UK cases occurred over 30 years ago. Neurosurgical instruments used on possible carriers of CJD are now handled in accordance with the ACDP TSE Working Group guidance. The other two cases were reported from Switzerland and resulted from the reuse of contaminated electrodes. All neuroelectrodes are now single-use.

There have been no reported cases of patient-to-patient transmission of vCJD via current techniques of surgery, laryngoscopy or endoscopy. The three documented UK cases of possible iatrogenic transmission of vCJD relate to blood transfusions, which are excluded from the remit of this guidance. Nevertheless, surgical transmission of vCJD cannot be ruled out as a risk to public health in the future. The potentially long incubation period makes it possible that patients may have become infected as a result of interventional procedures, even though no cases have been reported in recent years. Without the means to link between diagnosed cases, through instrument tracking, it is not possible to identify potential transmission events.

2.4.5 Advisory groups

A number of advisory committees, expert groups and academic units are actively involved in addressing a variety of issues relating to CJD (see appendix B). The issues range from developing the scientific basis of our understanding of the disease, to improving decontamination practices across the NHS, to minimising the risk of transmission. The Institute has made every effort to coordinate its activities with these groups and to ensure that this guidance takes account of, and builds on, their work. Many of the members of the Committee advising the Institute on CJD are also members of the other committees, working groups and academic units. In addition, the Institute has been represented on a number of these groups.

[2] Detailed consideration of costs was not possible for these areas.