Although Creutzfeldt-Jakob disease (CJD) is rare, the disease is far from unknown and requires special reprocessing protocols. CJD is a form of transmissible spongiform encephalopathies (TSEs) also known as prion diseases. These unique pathogens are resistant to standard sterilization protocols. ANSI/AAMI have very specific recommendations related to the processing of devices contaminated with tissue from known or suspected CJD high-risk patients.
TSE’s and Prion Diseases
TSE’s are a family of rare progressive neurodegenerative disorders that affect both humans and animals. TSE's are distinguished by progressive nerve damage over long incubation periods. The damaged nerve cells contain tiny vacuoles (membrane-bound sacs within a cell’s cytoplasm) in the brain giving it a “sponge-like” appearance under a microscope. This type of damage leads to impaired brain function affecting a person’s personality, memory and behavior. TSEs are often accompanied by intellectual decline and movement abnormalities, such as ataxia. Symptoms usually develop during adulthood and gradually worsen causing death within several years or even a few months.1 Prions are believed to be the causative agents of TSEs. Prions are a disease-causing form of a protein particle called cellular prion protein (PrPc). PrPc's are mainly found on the surface of cells in the central nervous system, however it is also located in other bodily tissues. Studies suggest that this protein plays a protective role in cells and helps them respond to oxygen deficiency. PrPc's are smaller than viruses and clusters of them can only be seen through an electron microscope. Most noteworthy, prions are unique in that they do not contain nucleic acid, unlike bacteria, fungi, viruses. Therefore these particles are resistant to sterilization procedures that destroy pathogens by breaking down nucleic acid. Furthermore, because prions are an abnormal version of a normal protein that is already coded for in the body, they do not trigger a host immune response, as other pathogens, so the disease is hard to detect in early stages.2
Types of CJD
In 1996 there was an outbreak of variant Creutzfeldt-Jakob disease (vCJD), a prion disease that was first identified in the United Kingdom. There is now strong scientific evidence that the agent responsible for the outbreak of prion disease in cows, bovine spongiform encephalopathy (BSE or 'mad cow' disease), is the same agent responsible for this outbreak of vCJD in humans. The other form of CJD is known as classic CJD (simply called CJD). It has different clinical and pathologic characteristics than vCJD. Each disease also has a unique genetic profile of the prion protein gene. Both disorders are invariably fatal brain diseases with unusually long incubation periods measured in years, and are caused by prions.3 Classic CJD was first recognized around 1920s, and is believed to be a spontaneous transformation of normal prion proteins into abnormal prions. This sporadic disease occurs worldwide, including in the United States, at a rate of roughly 1 to 1.5 cases per 1 million population per year. Classic CJD typically occurs in persons over 50 years of age, with an annual rate in the over 50 population of approximately 3.4 cases per million. While the majority of cases develop spontaneously, about 5-15% of CJD cases are due to inherited mutations of the prion protein gene. These inherited forms include Gerstmann-Straussler-Scheinker syndrome and fatal familial insomnia.4
What is the Occurrence Rate of CJD?
Cases of vCJD in the U.S. are extremely rare, (3 patients historically that also spent time in the UK and Saudi Arabia), but there have been anywhere from 172 to 478 cases per year of classic CJD over the past 20 or so years. Here are some statistics from the Center for Disease Control (CDC) going back to 1979.
Creutzfeldt-Jakob disease deaths and age adjusted death rate, United States, 1979-2013
Deaths obtained from the multiple cause-of-death data for 1979-1998 are based on ICD-9 codes, and those beginning in 1999 are based on ICD-10 codes with available computerized literal death certificate data. Death information was also obtained from other surveillance mechanisms; data include familial prion diseases. Rates are adjusted to the US standard 2000 projected population.5
Reprocessing Contaminated Assets Summarized
The ANSI/AAMI ST79 guidelines and recommendations related to devices and equipment contaminated with high-risk tissues (defined as brain [including dura mater], spinal cord, and eye tissue) from high-risk patients (i.e., those known or suspected to have CJD) provide:
- Specific sterilization parameters for contaminated surgical instruments that are constructed so that cleaning procedures result in effective tissue removal.
- Specific sterilization parameters of contaminated instruments that are difficult to clean.
- Detailed procedures for cleaning noncritical surfaces and equipment contaminated with high-risk tissue
Additionally, the guidelines recommend:
- Impossible to clean items should be discarded.
- To minimize drying of tissues and body fluids on the object, devices should be kept moist until cleaned and decontaminated.
- Immediate-use steam sterilization (formerly known as flash sterilization) should not be used for reprocessing these devices.
- Contaminated items that have been in contact with high-risk tissue and have not been processed according to these recommendations (e.g., medical devices used for brain biopsy before diagnosis) should be recalled and appropriately reprocessed.
- A tracking system should be in place that permits recall of devices used on high-risk tissue and high-risk patients. This tracking system should identify:
- of the patient on which the devices were used,
- the date they were used, the procedure performed
- and the surgeon’s name
(For facilities that do not have an automated system, recommendations for creating a manual system are detailed.)
- Use of power drills or saws that are likely to contact high-risk tissue should be avoided.
- Equipment that requires special prion reprocessing should be tagged after use. Clinicians and reprocessing technicians should be thoroughly trained on the proper tagging of equipment and on the special prion reprocessing protocols.6
CDA FDA Health Advisory: 3 Recommendations
5 Decontamination Mistakes
Failure to follow appropriate sterile processing standards endangers your patient safety
1Robertson, Sally. “What is a Prion?” Updated July 20, 2015. Available at: http://www.news-medical.net/health/What-is-a-Prion.aspx. Accessed January 16, 2017
2Centers for Disease Control. “Prion Disease”. Updated Feb. 5, 2015. Available at: https://www.cdc.gov/prions/index.html. Accessed January 17, 2017.
3Centers for Disease Control. Variant Creutzfeldt-Jakob Disease (vCJD) – About vCJD. Updated October 7, 2014. Available at: https://www.cdc.gov/prions/vcjd/about.html. Accessed January 17, 2017.
4, 5Centers for Disease Control. “Creutzfeldt-Jakob Disease, Classic (CJD) – Occurrence and Transmission”. Updated November 10, 2015. Available at: https://www.cdc.gov/prions/cjd/occurance-transmisison.html. Accessed January 23, 2017.
6Association for the Advancement of Medical Instrumentation. Comprehensive guide to steam sterilization and sterility assurance in health care facilities. ANSI/AAMI ST79:2010 & A1:2010 & A2:2011 & A3:2012 & A4:2013. www.aami.org, p.166