Classic Creutzfeldt-Jakob Disease in Canada: Quick Reference Guide 2007

Introduction

In December 2004, the Public Health Agency of Canada (PHAC) convened a special meeting of the Advisory Committee on Infection Prevention and Control for Creutzfeldt-Jakob Disease, to review and revise as necessary the « 2002 Infection Control Guideline for Classic Creutzfeldt-Jakob Disease in Canada ».

A PHAC International CJD Scientific meeting, where the most up-to-date scientific information on CJD and its iatrogenic transmission was reviewed, preceded this meeting. This document represents clarification and revision of components of the « 2002 CJD Infection Control Guideline » based on information available at the time of the 2004 PHAC International CJD Scientific Meeting. See the « 2002 CJD Infection Control Guideline » for complete recommendations.

The most effective, safe, and efficient means of preventing iatrogenic transmission of CJD are to identify high-risk patients before an invasive procedure, in order to implement the required infection prevention and control measures, and to have a system for instrument tracking (Section 3, page 6).

Note: Infection prevention and control measures to prevent or minimize exposure to variant CJD (vCJD) will not be addressed in this document. If a case of vCJD is clinically suspected or diagnosed, for specific infection prevention and control measures, the practitioner should consult with the Nosocomial and Occupational Infections Section, Blood Safety Surveillance and Health Care Acquired Infections Division, Centre for Infectious Diseases Prevention and Control, Infectious Diseases and Emergency Preparedness Branch, Public Health Agency of Canada, at the following number: (613) 952-9875.

1.0 Is the Patient a Potential CJD Transmitter?

1.1 High-risk Patients

Patients considered to be at high risk of transmitting CJD iatrogenically are those diagnosed, prospectively or retrospectively, with:

• CJD - confirmed, probable, or possible CJD, familial CJD, Gerstmann-Sträussler-Scheinker disease (GSS), or fatal familial insomnia (FFI) depending on pathological, laboratory, and clinical evidence and following the Surveillance definitions for Classic CJD^{Footnote 1}.
• Suspected CJD - undiagnosed, rapidly progressive dementia and CJD not ruled out.
• Asymptomatic carrier of genetic transmissible spongiform encephalopathy (TSE) - a person who displays no symptoms or signs of TSE, but meets one or more of the following criteria :
  1. The person has been confirmed by genetic testing to carry a genetic mutation causative of familial CJD, GSS, or FFI;
  2. The person has at least one first-degree relative who has been confirmed by genetic testing to carry such a mutation, with or without pathologic confirmation of TSE;
  3. The person has two or more first-degree relatives who have been diagnosed with either confirmed or probable TSE, with or without confirmation by genetic testing.

Step 4 outlines appropriate procedures for managing instruments that have been in contact with high-risk patients, depending on the potential infectiousness of the tissue contacted.

To minimize the risk of transmitting CJD, elective procedures in high-risk patients (involving high-risk or low-risk tissues) should be well justified and carefully planned in advance.

1.2 At-risk Patients

The following patients are at risk of iatrogenic CJD:

• Recipients of human tissue derived pituitary hormone treatment (either growth hormone or gonadotrophin).
• Recipients of a dura mater graft (until 1992 for Lyodura grafts, until 1997 for Tutoplast Dura grafts).
• Recipients of a corneal graft originating in a jurisdiction that does not require graft donors to be screened for neurological disease.
• Patients who have been exposed, via contact with instruments, to high-infectivity tissue of a confirmed CJD patient.

The Working Group considers, after examining the available evidence, that the risk of transmission via instruments used on at-risk, asymptomatic patients is negligibly low, and therefore, recommends such instruments be routinely decontaminated and then reused. This represents a change from the « 2002 CJD Infection Control Guideline ».

Screening procedures should be performed to identify high-risk patients, and not to identify at-risk patients. A patient who self-identifies as being at-risk should be evaluated clinically for evidence of CJD.

2.0 Was Infectious Tissue Contacted?

The procedures recommended for managing instruments used on high-risk patients depend on the potential infectivity of the tissue contacted. Using evidence from animal studies and reports of infection through iatrogenic exposure, human tissue is classified into three categories, according to its risk of transmitting CJD. This information was updated based on the 2006 WHO Guidelines on tissue infectivity distribution in transmissible spongiform encephalopathies and is subject to change as further information becomes available.

In this update of the « 2002 CJD Infection Control Guideline », infectivity for cornea, optic nerve, and retina has been differentiated. Trigeminal and spinal ganglia have been classified as high-infectivity tissues. Dental pulp has been moved from low-infectivity to no detected infectivity based on recent experiments that did not detect the abnormal prion protein in dental pulp of patients with human TSEs. Serous exudates have been removed.

3.0 Which Instruments Were Used?

It is recommended to:

• Limit as much as possible the number of instruments used for any procedure.
• Use disposable rather than reusable instruments whenever possible and especially when in contact with high-infectivity tissue.
• When using reusable instruments, choose, whenever possible, those that can tolerate the rigors of CJD decontamination.
• Track use of reusable instruments.

3.1 Instrument Identification

Without detailed information as to which reusable instruments were in contact with potentially infectious tissue, the only way to eliminate all risk of iatrogenic transmission is to discard all potentially contaminated instruments, creating considerable waste.

Without such information, the opportunity to reduce the risk of transmission by instruments already in circulation - a risk to which some patients have already been exposed - is lost.

To reduce or eliminate such risk without waste, it is strongly recommended that all reusable instruments be tracked. Technology is now available for tracking instruments, though not widely used, and more effective technology is being developed.

Some sample tracking measures are listed below in order, roughly, of increasing effectiveness and decreasing feasibility. Immediate adoption of the most effective feasible measures is recommended, with the addition of even more effective methods as soon as these become feasible. Facilities that have not yet established a full tracking system (measure 1) should, at a minimum, segregate those instruments used on high-infectivity tissue (measure 2).

1. Identify - for example, by means of a colour code or a bar code - those sets of reusable instruments used only on:
   • brain and neuro/ortho spine;
   • retina/posterior eye.
   Keep these sets separate from other sets.
2. Within a set of instruments, identify those used only on high-infectivity tissues; Keep these specific instruments separate from the others.
3. Identify - for example, by means of a bar code - each individual instrument and the set to which it belongs. Associate the records of the use of this individual instrument with the records of patients on whom it was used.

4.0 Recommended Actions

We recommend some combination of the following measures to manage or reduce the risk of iatrogenically transmitting CJD infection through reused instruments.

4.1 Discard

To discard means to assure an instrument cannot possibly transmit infection to another patient. Incineration is the most unambiguous means of doing so. Note, however, there is evidence that prions can survive very high temperatures.

Where incineration is not available, an acceptable alternative is CJD decontamination (see below) followed by disposal in a landfill.

4.2 CJD Decontamination

We recommend, where appropriate, a combined method of CJD decontamination in four steps:

1. Clean thoroughly;
2. Soak in 1N sodium hydroxide (NaOH) for 1 hour;
3. Thoroughly rinse;
4. Sterilize in a prevacuum-method autoclave at 134ºC for 60 minutes.

Acceptable substitutions for steps 2 and 4 include:

2. Substitute 2% NaOCl (20,000 ppm available chlorine) for 1N sodium hydroxide (NaOH); 4. Sterilize in a prevacuum-method autoclave at 134ºC for 18 minutes rather than 60 minutes.

Notes:

• Instruments made of high-quality stainless steel can tolerate CJD decontamination using NaOH.
• Instruments that contain plastic or electronic devices, such as bronchoscopes, cannot tolerate CJD decontamination.
• Instruments that contain both steel and other metals, and particularly aluminum, should never be exposed to NaOH.

Ideally, decontamination procedures shown to deactivate prions would be used on all instruments no matter which patients they were used on or what tissues they contacted. Unfortunately, the only available procedures for which there is evidence of effective deactivation cannot be routinely used as they are potentially damaging to many instruments. We do not believe, based on the evidence, that autoclaving at 134°C for 18 minutes by itself suffices to deactivate prions, and hence do not recommend this as a routine procedure to prevent CJD transmission.

4.3 Routine Reprocessing

Routine decontamination and sterilization/disinfection in the recommended Canadian Standards Association (CSA) specified manner.

4.4 Quarantine

After routinely reprocessing separately from other instruments (see Decision algorithm, p. 13), store instruments in dry conditions. Do not reuse unless a diagnosis is made that eliminates the possibility that the patient on whom the instruments were used had CJD. A confirmed diagnosis other than CJD, either clinical or pathological, or a postmortem examination excluding CJD, is required to take instruments out of quarantine. A brain biopsy that is negative for CJD, in the absence of a confirmed alternate diagnosis, does not suffice to take instruments out of quarantine.

5.0 Decision Algorithm (textual Version)

5.3 At-risk Patients for CJD

In this update of the « 2002 CJD Infection Control Guideline », incineration or CJD decontamination is no longer recommended for the high-infectivity tissues of at-risk patients.

6.0 Decision Algorithm (graphic Version)

Text Equivalent - Decision Algorithm

7.0 References

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