Healthcare constantly evolves to improve the quality of care provided to patients. In line with this continuous quality improvement, the practices of sterilization and disinfection currently are being scrutinized regarding their effectiveness.

For more than 50 years, the determination of how to process a medical device has been based on the Spaulding classification. According to this system, semicritical items are medical devices that contact mucous membranes and, at a minimum, must be subjected to a high-level disinfection (HLD) process, which would be expected to destroy all microorganisms other than large numbers of bacterial spores.

Although processing all semicritical items using HLD has been acceptable for many years, this practice is being challenged based on research showing that some pathogens are resistant to HLD. Research has shown that neither glutaraldehyde nor ortho-phthalaldehyde significantly reduce the infectivity of the human papillomavirus type 16.1 

In addition, real-world research has demonstrated that adhering to instructions for use (IFUs) for complex medical devices can be difficult and time consuming. Many flexible endoscopes are considered complex because they have one or more long narrow lumens with numerous parts, resulting in more than 100 steps to process.2 Coupled with demands to quickly process items, processing professionals are faced with major challenges.

Low-temperature sterilization is now available and can sterilize medical devices in a short amount of time. Most importantly, processing semicritical devices via HLD has resulted in infectious outbreaks. Therefore, finding other means of microbial destruction is necessary. Industry leaders have assessed the Spaulding classification and are recommending that semicritical items be transitioned from HLD to sterilization when possible.3 

The original Spaulding classification has three levels of disinfection and sterilization classifications for medical device processing:

  • Critical devices enter sterile tissue and must be sterile.

  • Semicritical devices contact mucous membranes and should be sterilized, if possible. However, if sterilization is not feasible, the device, at a minimum, must be subjected to an HLD process that would be expected to destroy all microorganisms except for large numbers of bacterial spores.

  • Noncritical devices come in contact with intact skin and require low-level disinfection.

The Spaulding classification has proven to be effective and logical; however, studies involving viruses, mycobacteria, and protozoa have emerged that challenge the current definitions and expectations of HLD and low-level disinfection. In addition, when the Spaulding classification was developed in the 1950s, many complex medical devices that contact the mucous membrane were not invented and most low-temperature sterilization modalities were not available.4 

Many differences exist between HLD and sterilization. One recognizable difference is that sterilized items are dry and packaged, while those that have undergone HLD are unpackaged and wet after the process. The most significant difference between HLD and sterilization, however, is their effectiveness. HLD is a process that kills all microbial organisms but not necessarily large numbers of bacterial spores, whereas sterilization is a validated process used to render a device free from viable microorganisms and provide a sterility assurance level that cannot be achieved with HLD. Although HLD does provide a 6-log reduction in microbial contamination, sterilization typically can offer twice that amount (i.e., a 12-log reduction).5 

This higher quality assurance level of sterilization is accompanied by quality process monitors that verify the efficacy of the sterilization process.

This higher quality assurance level of sterilization is accompanied by quality process monitors that verify the efficacy of the sterilization process. Sterilizers are tested at least daily with a process challenge device containing a biological indicator (BI) that provides a known, highly resistant challenge to the sterilization process (106) and is a direct measure of the lethality of a sterilization cycle. This method of challenging the sterilization process is so reliable that sterilizer manufacturers use BIs as part of the validation of their sterilization cycles during half-cycle validation testing.5 

Sterilization cycles are monitored with physical monitors that record critical sterilization parameters, such as time and temperature. These parameters are reviewed for acceptance against validated specifications before releasing the load, and the records are maintained.5 

Every item that undergoes sterilization has both internal and external chemical indicators (CIs). The external CIs are used to indicate that the package has been exposed to the sterilization process and to distinguish between processed and unprocessed packages. Different types of internal indicators, which are designed to react to two or more of the critical process variables and intended to indicate exposure to the sterilization process, may be used. These indicators must meet the qualifications described in the standard ANSI/AAMI ST79:2017.5 

The chemical process monitors available for HLD are CIs that measure either the minimum effective concentration, which is the minimum concentration of a high-level disinfectant that achieves the claimed microbicidal activity, or the minimum recommended concentration, which is the minimum concentration at which the manufacturer tested the product and validated its performance.6 Currently, no standards exist for these chemical process monitors. When HLD is performed in an automated system, most systems also provide a printout showing the cycle parameters. Manual systems, however, do not have a method of recording HLD parameters.6 

In 2013, outbreaks involving multidrug-resistant organisms (MDROs) associated with duodenoscopes were reported. Transmission has been documented, and reports have surfaced of other types of contamination of patient-ready endoscopes. Several facilities experiencing MDRO and duodenoscope-related outbreaks changed their scope-processing procedures, including following IFUs, adhering to best practices, and transitioning from HLD to terminal sterilization with ethylene oxide.

In the case of one outbreak, the transition to sterilizing with ethylene oxide was attributed with halting the endoscope-related transmission.7 This outbreak was so significant that in May 2015, the Food and Drug Administration (FDA) began seeking scientific evidence and expert opinion related to reprocessing duodenoscopes. The agency performed investigations, published alerts, announced recalls, and convened the Gastroenterology-Urology Devices Panel of the Medical Devices Advisory Committee.8 The FDA further sought to inform rigorous practicable reprocessing protocols that would enhance the safety margin of endoscopic retrograde cholangiopancreatography procedures.9 In 2015, the agency issued a safety communication in which it recommended that duodenoscopes, when possible and practical, should be sterilized due to the greater margin of safety provided.9 

Most flexible endoscopes are considered semicritical medical devices and, therefore—according to the Spaulding classification—can undergo HLD. In response to outbreaks and other urgent issues, including whether the Spaulding classification needed to be reassessed, the Association for the Advancement of Medical Instrumentation (AAMI) held a meeting in September 2017. The meeting involved more than 40 stakeholders representing healthcare professional organizations, manufacturers, testing labs, independent research groups, academia, patient and clinical end users, the FDA Center for Devices and Radiological Health, and the Centers for Disease Control and Prevention.

When the Spaulding system was designed 50 years ago, semicritical items rarely, if ever, penetrated sterile tissue and healthcare did not have an adequate appreciation for the infection risk associated with endoscope reprocessing.

When the Spaulding system was designed 50 years ago, semicritical items rarely, if ever, penetrated sterile tissue and healthcare did not have an adequate appreciation for the infection risk associated with endoscope reprocessing.

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During the meeting, experts presented reasons for HLD failure, including poor cleaning practices and lack of training. Highlights from the presentations included the following3:

  • William Rutala, PhD, MS, MPH, director of the statewide program for infection control and epidemiology in North Carolina and professor of medicine at the University of North Carolina in Chapel Hill, concluded that HLD of endoscopes provides no margin of safety. HLD provides a 6-log reduction in microbial contamination, while sterilization offers a 12-log reduction. He further noted that although HLD removes or inactivates 10 to 100 million spores, sterilization kills 1 trillion spores. Rutala proposed that the Spaulding classification for critical items should be modified from “direct contact with sterile tissue” to “direct or secondary/indirect contact with sterile tissue.” He further noted that when the Spaulding system was designed 50 years ago, semicritical items rarely, if ever, penetrated sterile tissue and healthcare did not have an adequate appreciation for the infection risk associated with endoscope reprocessing, with endoscopes used primarily for diagnostic purposes. Rutala summarized the problems with reprocessing endoscopes with HLD as follows: “If the margin of safety is so small that perfection is required, then the design is too complex, and the process is too unforgiving to be practical in a real-world setting.”

  • Cori L. Ofstead, MSPH, president and CEO of Ofstead & Associates Inc., in Saint Paul, MN, presented data from studies conducted during 2008 to 2017. These real-world studies showed that although HLD should work, many barriers to effective reprocessing exist, including damaged scopes; use of defoaming agents and lubricants that cannot be removed from scopes (and that harbor biofilm); rinsing with contaminated water; failing to dry endoscopes; storing endoscopes in unventilated storage cabinets; using bare hands and dirty containers to transport endoscopes; neglecting to clean, disinfect, and perform preventive maintenance on reprocessing equipment; and not performing sufficient monitoring of reprocessing effectiveness. Ofstead's research team also has found that healthcare facilities lack sufficient time to perform all of the necessary processing steps, to the point that that patient safety is compromised. In addition, complex device designs and IFUs make it difficult for staff to adhere to all steps in endoscope reprocessing, meaning that “HLD is cutting it too close.”

  • Michelle Alfa, PhD, MSc, BSc, principal investigator at St. Boniface Research Centre in Winnipeg, Canada, presented findings showing that repeated use of endoscopes leads to gradual accumulation of debris, which can lead to microbial survival following disinfection. Cleaning remains the most important part of the disinfection or sterilization process, said Alfa. She recommended transitioning to sterilization for all endoscopes and emphasized the importance of sterile storage of endoscopes that secondarily contact sterile body sites. Unless these measures are taken, said Alfa, survival of bacteria will occur.

Sterilization has a higher level of assurance than HLD and provides a finished product that is packaged and able to be stored for later use. HLD provides a finished product that is wet and unpackaged.

At the meeting's conclusion, the stakeholders agreed that cleaning is the most important part of the process, processing personnel must be trained and capable of demonstrating competencies, and all IFUs must be followed. Further, while recognizing that the change would need to happen gradually, the stakeholders concluded that the industry should move from HLD to sterilization of endoscopes.3 

Three guidelines from the Association of periOperative Registered Nurses recommend sterilization over HLD for semicritical medical devices: the guideline for manual chemical high-level disinfection,1 guideline for cleaning and processing flexible endoscopes,10 and guideline for sterilization.11 The guideline for sterilization states that pathogens exist that are resistant to HLD, including, but not limited to, small nonenveloped viruses (e.g., parvoviruses, coxsackieviruses, other enteroviruses, hepatitis A, norovirus) and resistant bacteria (e.g., Mycobacterium tuberculosis, Mycobacterium avium, Mycobacterium abscessus, Mycobacterium fortuitum, Mycobacterium chimaera). This guideline11 concurs with the findings from the AAMI stakeholder meeting—that a lack of compliance with sterilization and disinfection guidelines have led to numerous infectious outbreaks and that many have been related to semicritical items.

For sterilization or HLD to be effective, all surfaces of an item must be thoroughly cleaned to permit full surface contact. Some high-level disinfectants act as fixatives and may result in organic soil and blood becoming fixed to the surfaces, which is another reason for meticulous cleaning of a device.1 

In addition to scientific evidence supporting the transition from HLD to sterilization, operational, safety, and quality reasons also make this transition compelling.

As described above, sterilization has a higher level of assurance than HLD and provides a finished product that is packaged and able to be stored for later use. HLD provides a finished product that is wet and unpackaged.

Because they are not packaged, storing and handling items that have undergone HLD requires more diligence to prevent contamination. Following the HLD process, items should be identified as “patient ready” to prevent the use of unprocessed items. If an item is not packaged, a storage cabinet should be used to protect the device from contamination and damage.12 Unpackaged items should be transported in a manner that protects them from contamination, including the use of latex-safe gloves. In accordance with hospital policy, unpackaged items often have a short storage time (typically based on days). In some cases, this may require an item to be processed shortly before use, resulting in an item not being readily available. In other cases, this may require the item to be processed more often, which can lead to added wear on the device.12 

HLD involves the use of automated (e.g., automatic endoscope reprocessors [AERs]) or manual systems. Automated HLD processors have proven to be more effective than a manual system and are recommended. Figure 1 in the online data supplement (available at https://aami-bit.org/loi/bmit) shows the differences in steps between the three processes of sterilization, manual HLD and an automatic HLD system.1 

A manual HLD system presents more difficulties and chances of errors than an automated system. Many of the automated systems are designed to provide consistency, reliability, productivity, reduced chance of employee exposure to chemicals, and documentation of cycles. As high-level disinfectants are liquids, chemical spills are possible. The healthcare facility must ensure that employees are protected from exposure to these chemicals and provide the necessary personal protective equipment. Regardless of the HLD system used, the correct utilities must be available. To reduce the chance of a spill, the high-level disinfectant should be located as close as possible to a sink.1 

Another drawback to a manual HLD system is that inconsistencies frequently exist among different technicians processing medical devices. Even for the same technician processing a medical device at different times during the day, inconsistencies can occur.

After a bottle of high-level disinfectant is opened, an expiration date must be added. This date is based on the IFU from the disinfectant manufacturer. When a high-level disinfectant is poured into a secondary container, that container must be labeled with the disinfectant name and expiration date. The secondary container must be clean and closed. All containers used for manual disinfection require thorough cleaning between uses.

HLD requires exposure for a specific time and temperature range. In a manual system, ensuring the temperature is reached and maintained is cumbersome. An additional complication is that personnel must document this information manually.6 

Without proper rinsing, liquid chemical disinfectants can leave a toxic residue that can cause patient injury. Reports of these injuries have included toxic anterior segment syndrome, anaphylaxis, and bowel injury. After HLD, the final rinses should be performed using critical water to prevent contamination. Critical water is extensively treated, usually by a multistep process such as softening, deionization, reverse osmosis, or distillation, to ensure that microorganisms and inorganic and organic material are removed from the water. The high-level disinfectant IFU provides specific information on the amount of rinses to use. Each rinse requires fresh water to prevent recontamination with water containing HLD.6 

After disinfection is complete and the item is thoroughly rinsed, it also must be thoroughly dried to prevent contamination. The design and use of flexible endoscopes present a greater chance of contamination. Storing flexible endoscopes with residual fluid has been shown to promote the growth of Gram-negative bacteria and other pathogens. Research also has shown that fully reprocessed endoscopes can harbor water pathogens such as Pseudomonas aeruginosa and Stenotrophomonas maltophilia if not dried before storage.

In a study conducted among three hospitals, fluid was detected in the channels of 45% of stored flexible endoscopes.13 The researchers concluded that sterilizing scopes would alleviate the problems related to inadequate drying and storage of flexible endoscopes, as well as result in a less hospitable environment for microbes that thrive in wet conditions. Of important note, most AERs do not have sufficient drying times to adequately dry endoscopes; thus, an additional manual drying step is necessary.

Transitioning from HLD to sterilization requires effective planning, communication, and record keeping. Before the transition begins, all stakeholders should be actively engaged in the process. This is best accomplished by forming an interdisciplinary team with leadership from surgery and central service, as well as a surgeon and a representative from infection prevention. This team needs to be consulted and communicated with throughout the transition. Gaining the approval and support of hospital administration for this team also is important. Leadership should be informed of the benefits and potential challenges of the transition.

The time to obtain a sterilized item is immediate, whereas an HLD item may require additional time to undergo reprocessing depending on how long it has been stored.

The interdisciplinary team can perform a risk assessment to determine whether sterilization is feasible and if transitioning to sterilization would improve the quality of care provided. The advantages, disadvantages, and implementation process should be explained to facility leadership. The advantages and disadvantages of both sterilization and HLD are summarized in Tables 1 and 2.

Table 1.

Advantages of sterilization and high-level disinfection (HLD)

Advantages of sterilization and high-level disinfection (HLD)
Advantages of sterilization and high-level disinfection (HLD)
Table 2.

Disadvantages of sterilization and high-level disinfection (HLD)

Disadvantages of sterilization and high-level disinfection (HLD)
Disadvantages of sterilization and high-level disinfection (HLD)

Obtaining leadership approval and support is a critical part of this process. Issues to consider include:

  • The level of disease transmission risk for items processed by HLD versus sterilization.

  • Documented validation testing for a specific HLD or sterilization modality.

  • Storage time and requirements of items processed by HLD compared with items sterilized in sterilization packages. Of note, compared with sterilization, HLD requires more labor, results in less rapid availability of devices, and results in additional processing and, therefore, more wear on endoscopes.

  • Chemical safety for both HLD and low-temperature sterilization. The safety data sheets for these chemicals provide employee and patient safety considerations.

  • The complexity of the processes. The more complex a process, the more it is prone to errors.

  • Whether the quality monitors designed for HLD or sterilization provide the necessary level of assurance for patient safety.

  • Examining the processing/turnaround time of each process.

  • Reviewing the methods for labor time and processing time, excluding automated processes.

  • Whether the acquisition time is a critical factor. The time to obtain a sterilized item is immediate, whereas an HLD item may require additional time to undergo reprocessing depending on how long it has been stored.

  • Damage to an item caused by the process.

  • When switching from a high-level disinfectant to another chemical process, the presence of residue may need to be addressed.

  • Regular and long-term maintenance and calibration of sterilization equipment.

  • Risks associated with the malfunction of sterilization equipment (to the medical device or personnel).

The medical device IFU provides critical information as to whether it has been validated for sterilization. If the manufacturer conducted a validation study, they may be able to provide documentation on the type of sterilization for which the device is validated, as well as the type of cycle to use. Many medical devices also have accessories (e.g., containment device or tray, attachments) that should be included in this process. All sterilization information should be available in a manner that can be recorded and referenced.5 

If a new sterilization modality is being implemented, the packaging and quality monitors (i.e., CIs and BIs) need to be reviewed to ensure that they also are validated for that type of sterilization. Training of central service staff on the sterilization system, new packaging, and quality monitors will be required. Personnel using the medical device also require training on the packaging system and quality monitors.5 

When transitioning from HLD to a sterilization method, high-level disinfectant residue may exist on the device. Before proceeding, check with the device manufacturer and sterilizer manufacturer if this is a possibility. If so, obtaining documented information on how to avoid or eliminate the residue is critical.

As validations are confirmed and recorded for reference, the interdisciplinary team should be informed of the progress.

Moving from an HLD process to sterilization may require a containment device or instrument tray to securely hold the item to prevent damage and to completely expose all surfaces of the item to the sterilant. If a new type of containment device or instrument tray is used to package the item, it must be validated for that type of sterilization. In addition, the cleaning instructions need to be reviewed and communicated to central service staff. When transitioning an item to sterilization, the IFU may require special attachments or positioning. Sterilization qualification testing for an item may be performed.

Training of central service staff on the sterilization system, new packaging, and quality monitors will be required. Personnel using the medical device also require training on the packaging system and quality monitors.

The preparation instructions in the central service department will need to be changed. If an instrument tracking system is used, each medical device will need to be changed to reflect the change to sterilization as it occurs. Using pictures to show the placement of a cap or adaptor is helpful.

Central service staff should undergo training for each medical device. In addition, the direct users (e.g., surgeons, operating room staff) need to be informed of these changes and also may require training. The changes with the greatest impact on their functions are:

  • Packaging. The user needs to be aware of the packaging so they can be prepared to aseptically open the package.

  • Turnaround time. Knowledge of turnaround time will be needed for scheduling cases.

  • Clear identification items. Because they are not packaged, items that undergo HLD are visible and can be clearly identified. On the other hand, sterilized items are packaged and therefore not visible. Labels on packages containing sterilized items inform users of the contents.

  • Storage. Packaged sterilized items often are stored in different locations than those that undergo HLD. All staff members need to be aware of the correct location for stocked items.

  • Quality monitors. The direct user needs to know how to identify an item that has successfully undergone sterilization.

The transition to sterilization should occur in an organized manner, with all stakeholders, especially the surgical department, kept informed of the progress.

Keeping the infection prevention department head and committee informed as medical devices transition from HLD to sterilization is important. This may be achieved by adding an agenda item to an upcoming infection prevention committee meeting.

Going forward, as new medical devices are purchased, the product review should include the sterilization modality. This is accomplished by reviewing the IFU for sterilization information. If the semicritical medical device does not provide a method of sterilization, it may not be approved for purchase and use. However, of important note, some essential semicritical medical devices may lack a sterilization validation claim. Until an alternative emerges, these items will need to be purchased.

A policies and procedures document should be developed with the interdisciplinary team. The document should clearly state that when available, sterilization is the preferred method for reprocessing semicritical items. These policies and procedures will support the requirement of a sterilization claim for further purchases of semicritical items and should be supported and approved by the infection prevention committee and administration.

A multitude of benefits exist for transitioning from HLD to sterilization for semicritical items. During the initial transition period, completely transitioning all semicritical items to sterilization may not be possible. However, as new items are purchased, the implementation will expand. The transition to sterilization should occur in an organized manner, with all stakeholders, especially the surgical department, kept informed of the progress.

Although sterilization provides a higher patient care standard, it also must be noted that sterilization alone will not erase all of the problems associated with contaminated medical devices. Research and real-world experience have emphasized the significance of following IFUs, AAMI standards, and other best practices; ensuring thorough cleaning, proper handling, and storage conditions; the need for training; and the need for adequate time to perform all reprocessing steps.

Transitioning to sterilization will take time and careful attention to detail. The bottom line is that by making this transition, patient care will be improved.

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Author notes

Susan G. Klacik, BS, CRCST, CCSMC, FCS, ACE, is a clinical educator for the International Association of Healthcare Central Service Materiel Management; she is based in Chicago. Email: [email protected]

Supplementary data