Sterilization vs. High-Level and Low-Level Disinfection [a 3-Point Comparison]

Key Takeaways

• There are three main levels of disinfection — high, intermediate, and low — each of which is used to process semi-critical and non-critical devices in healthcare facilities.
• High-level disinfection works by immersing a device in a liquid chemical agent, rinsing residual disinfectant from that device, and drying it off and placing it in storage.
• Sterilization is a different process than disinfection. Unlike disinfection, sterilization eliminates all contaminants from a device, including bacterial spores.
• Critical devices, such as surgical instruments, implants, and catheters, must be sterilized before use, as do most semi-critical devices.

In a 1939 paper, microbiologist Earle H. Spaulding introduced a system for determining which medical devices and instruments needed disinfection and which ones required sterilization. In it, he proposed that critical instruments would need to be subjected to more stringent disinfection protocols than non-critical patient care items. Today, this framework is fittingly known as Spaulding Classification and is used in healthcare facilities around the world for its patient safety benefits.

What does this system mean for your hospital or ambulatory surgery center (ASC)? Read on to find out the differences between high- and low-level disinfection and how both processes are distinct from sterilization.

Disinfection Levels Explained: High-, Intermediate- & Low-Level Disinfection

After medical instruments are used in procedures, they must undergo a thorough decontamination process before they can be safely reused. After a preliminary cleaning to remove soil, instruments move on to the second phase in the cycle: disinfection. In this step, chemicals are used to eliminate most contaminants, such as viruses and bacteria, from their surfaces.

For some medical devices, disinfection is an important step along the path that leads to sterilization (a similar yet entirely separate process). But did you know that the level of disinfection an instrument or other device requires depends on what it is and how it’s used?

• High-level disinfection involves using disinfectants that are capable of eliminating all microorganisms (except for a small number of bacterial spores) and inactivating any viruses present on a used piece of medical equipment. Given the nature of this type of disinfecting agent, high-level disinfection is reserved for semi-critical items, or those which contact mucous membranes or non-intact skin. Devices in this tier include respiratory therapy and anesthesia equipment, some endoscopes, laryngoscope blades, cystoscopes, esophageal manometry probes, anorectal manometry catheters, and diaphragm fitting rings.
• Intermediate-level disinfection uses agents to inactivate vegetative bacteria and most viruses and fungi, as well as the myobacteria responsible for tuberculosis. This type of disinfection will not eliminate bacterial spores and is overall less effective than its high-level counterpart. Intermediate-level disinfectants are suitable for non-critical devices and certain semi-critical items.
• Low-level disinfection refers to the use of a disinfecting agent that kills all vegetative bacteria as well as most viruses. Like intermediate-level disinfection, this type of disinfection will not eliminate bacterial spores. Considering this, low-level disinfectants are only suitable for use on reusable patient care devices that come into contact with intact skin only, such as blood pressure cuffs, stethoscopes, pulse oximeters, EKG leads, bedpans, crutches, wheelchairs, and exam tables.

What Is a High-Level Disinfectant?

A high-level disinfectant is a liquid chemical agent, cleared by the U.S. Food and Drug Administration (FDA), that eliminates all microorganisms on a medical device and is used to reprocess semi-critical devices that cannot tolerate sterilization. The FDA clears these agents as liquid chemical sterilants and grants the high-level disinfectant claim when a product achieves a 6-log kill of an appropriate Mycobacterium species at a shorter contact time than sterilization requires.

The FDA’s list of cleared formulations includes glutaraldehyde at 2.4% or higher, ortho-phthalaldehyde at 0.55%, hydrogen peroxide at 7.5%, and hydrogen peroxide combined with peracetic acid. Several products commonly found in healthcare facilities do not qualify, including alcohols, chlorine solutions, iodophors, quaternary ammonium products, and phenolics, which are not FDA-cleared for high-level disinfection of medical devices.

How Does High-Level Disinfection Work?

High-level disinfection is a timed chemical process with three stages that follow cleaning:

1. Immersion and contact: The device is fully immersed in the disinfectant for the amount of time specified on the label. If a device has internal channels, you must perfuse solution through every channel to clear air pockets and ensure the agent comes into contact with interior walls.
2. Rinsing: The next step is to remove residual disinfectant from the device. Sterile water prevents recontamination with organisms found in tap water. Facilities that rinse with filtered or potable tap water should follow with an alcohol rinse.
3. Drying and storage: Forced-air drying dramatically reduces bacterial contamination on stored devices by removing the moisture that allows organisms to multiply. Store the device so that it stays dry and protected from recontamination.

Many facilities run this process through an automated reprocessor rather than by hand. Automation standardizes these steps, reduces the risk of a technician skipping one, and limits staff exposure to concentrated chemicals. It’s important to note, though, that automated equipment has its own requirements, including correct connectors for each device and attention to the water filtration system, which can itself become a source of contamination.

What’s the Difference Between High-Level Disinfection and Sterilization?

We’ve already touched on this briefly, but it’s important to reiterate that while it’s also part of the overarching decontamination cycle, sterilization is an entirely different process than disinfection — no matter the level. Though an effective method of removing most harmful microorganisms that remain on critical devices after use, high-level disinfection doesn’t eliminate them completely.

Sterilization, on the other hand, does. There are many different methods for sterilizing medical instruments, but what they all have in common is the ability to eliminate all dangerous contaminants — including bacteria spores. Another key differentiator that separates sterilization from high-level disinfection is the use of specialized equipment. For example, one method of sterilization, steam sterilization, takes place in an autoclave: a piece of machinery that uses a combination of pressure, heat, and moisture to create an environment where harmful organisms can’t survive.

A Comparison: Sterilization, High-Level & Low-Level Disinfection

If you’re still unsure about what makes each of these three decontamination processes unique, the following chart breaks down the differences by what each process entails, the types of instruments and devices involved, and the methods used.

It’s important to keep in mind that there are multiple effective methods of sterilization in use today, which means that the exact process through which sterilization is achieved will depend on the method used. In the previous section, we established that steam sterilization relies on specially designed equipment to create an environment that’s lethal to viruses and bacteria (and their spores). Essentially, the same is true for other sterilization techniques, with the main differences found in the ways those environments are created.

For example, ethylene oxide sterilization takes place in large chambers and uses ethylene oxide gas to sterilize a wide range of instruments and devices. Gamma radiation kills microorganisms by breaking down their DNA, thus preventing division. And the dry heat technique leverages high-heat conduction to inactivate pathogens through oxidation.

Sterilization or Disinfection: Which Should You Use?

The Spaulding classification scheme answers this question for most devices: Critical devices require sterilization, while non-critical devices require low-level or intermediate-level disinfection. The open question is semi-critical devices: High-level disinfection is described as the minimum acceptable treatment rather than the recommended one.

Sterilization is the better option for a significant portion of semi-critical inventory. The CDC states that scopes entering normally sterile tissue should be sterilized before each use, with high-level disinfection as a fallback when sterilization isn’t feasible. Heat-stable scopes, including rigid ones, should be steam sterilized.

The Limits of Disinfection

High-level disinfection has multiple constraints that do not apply to steam sterilization:

• Spores survive. A properly disinfected semi-critical device may still have a small spore population, which is fine if the device comes into contact with mucous membranes, but unacceptable for anything entering sterile tissue.
• Disinfected devices come out wet and unpackaged. A sterilized instrument is packaged, and that package protects it until someone opens it. A disinfected device has no such protection, so your department needs a storage method to keep it dry, as well as a way to signal which devices are ready for use.
• Cleaning failures can be permanent. Some high-level disinfectants act as fixatives, binding organic soil and blood to a device rather than removing it. In these instances, an instrument that went into the solution with residual bioburden can come out with that bioburden fixed in place.

Is Your Healthcare Facility on the Right Track?

Steam sterilization technology plays a crucial role in the decontamination process by ensuring that medical devices and instruments are safe to use in future procedures. As such, it also serves an essential purpose in providing comprehensive care. Ready to put your ASC sterilization setup to the test? Take our free self-assessment to see whether your current setup sufficiently meets your needs.

Frequently Asked Questions

Does high-level disinfection kill C. diff?

High-level disinfection kills Clostridioides difficile in its vegetative form, but it does not consistently eliminate C. difficile spores. Those spores resist most common disinfectants, including alcohols and quaternary ammonium products. For environmental cleaning, the recommended approach is an Environmental Protection Agency (EPA)-registered sporicidal product such as a diluted bleach solution. For a reusable device contaminated with C. difficile, sterilization is the process validated to eliminate spores.

What’s the difference between cleaning, disinfection, and decontamination?

Cleaning removes visible soil from a device, but not the microorganisms left behind; disinfection destroys most pathogenic microorganisms, but not bacterial spores; and decontamination covers any process that makes a contaminated item safe to handle. Decontamination encompasses both disinfection and sterilization.

What happens if a device gets the wrong level of disinfection?

A device processed at the wrong level can introduce viable microorganisms into the next procedure, putting the patient at risk of a healthcare-associated infection. The wrong process can also damage the device, since some instruments cannot tolerate the heat or the chemistry involved. Facilities face regulatory exposure, as well, including reimbursement penalties and potential loss of accreditation.

What is a chemical sterilant?

A chemical sterilant is a liquid germicide cleared by the U.S. Food and Drug Administration (FDA) to destroy all microorganisms on a medical device, including bacterial spores. Facilities use them to process heat-sensitive devices that cannot go through an autoclave.