By Natalie Lind, CRCST, CHL, ACE
The buzzer rings on the dryer, you check the clothes, but the load is still damp. The
timer sounds on the stove and you check the cake in the oven. The directions say it should
be done now, but it needs a few more minutes. These timers with audible sounds are
indicators. In both cases the prescribed exposure times and temperatures had been met, and
yet an inspection indicated that each process was not yet successful.
Several times each day we use various indicators to aid in determining if requirements
have been met and that processes are being carried out correctly. We step on the scale to
check for indication of weight loss or gain. We check the gas gauge to see if we need fuel
in our vehicles.
Common indicators used in healthcare organizations are those that measure the
success--or failure--of the sterilization process. These indicators are particularly
important because, unlike many of the other processes we measure at work and at home,
there is no way to tell if our process was successful without them.
When a load is removed from the sterilizer, barring any major factors such as visible
wet packs, it is impossible to tell if the sterilization process was successful by visual
inspection. For that reason, we rely on sterilization indicator systems to provide us with
additional information about the success or failure of the process.
Sterilization indicators provide valuable tools that assess the quality of the goods
sterilized. These tools help prevent the release and use of items which may be unsafe.
It's easy to agree that the use of indicators is a positive form of quality assurance.
However, agreeing with the concept isn't quite enough. We must understand the basic
information about indicators and how to use them correctly.
Before using indicators, it's a good idea to review the common types associated with
the sterilization process and the function and purpose of each. Perhaps the most common
type of visual indicator used in sterilization is the chemical indicator (CI). CIs come in
a wide variety of sizes, shapes, and styles. Typically, they are broken into two
categories: external and internal.
External indicators are designed to provide the handler and user with a visual
indication that the item was exposed to a specific sterilant. This type of indicator aids
technicians in distinguishing processed from unprocessed item. They are often in the form
of tape, small cards, or dye spots on the exterior of medical packaging. External
indicators change color when exposed to a specific sterilant and that color change
provides evidence that the item was processed. It is important to remember that these
indicators do not prove that an item is sterile; they merely prove that an item came in
contact with the chosen sterilant.
Internal indicators also provide evidence of the presence of a sterilant. However,
internal indicators are placed inside each package prior to sterilization and measure the
penetration of the sterilant into the pack. This measurement is designed to provide the
package user with evidence that a sterilant was present inside the pack. Internal
indicators can detect packaging and placement failures such as air entrapment, incorrect
packaging selection and/or application, and improper loading of the sterilizer (Figure 1).
They may also detect mechanical failures such as air removal system failures.
As is the case with external indicators, internal chemical indicators do not prove that
an item is sterile. However, they are the only way to measure pack penetration in every
package. Most common methods of sterilization rely on direct contact between the sterilant
and the object being sterilized. A visual indicator that detects the presence of a
sterilant within the pack provides the user with some assurance that contact was made.
Most technicians use chemical indicators--dozens, even hundreds of times per shift.
They are easy to use and easy to read. In fact, the biggest danger in using chemical
indicators may be their familiarity. Because they are a part of every pack that is
assembled and sterilized, it is easy to take them for granted.
To provide the desired measurement, chemical indicators must be placed properly. While
this is easy for external indicators, there is a chance of error when placing internal
chemical indicators. Since the goal of the measurement process is to measure pack
penetration, internal chemical indicators should be placed at or near the center of the
pack. Placing them on top of the pack contents will not provide the same measurement of
pack penetration. Since the contents of each pack are different, the assembler should
place the indicator in a place where air would most likely be entrapped if it remained in
the package. That placement provides the best measurement for individual pack penetration.
In addition to placing indicators strategically within the center of the pack, each
indicator should be placed in a manner that makes it easily accessible for the user.
Long-handled indicators may need to be used for more complex packs.
One of the greatest challenges in the use of chemical indicators is maintaining the
ability to assess the outcomes of the indicators on and within every package. During the
course of one shift, sterilizer operators and product users will handle hundreds of
packages that contain indicators. The vast majority of all the packages handled will have
indicators that indicate no potential problems. It is easy to be lulled into complacency
when handling these familiar packages. When this happens, technicians and users often fail
to see the indicators themselves and instead become so accustomed to indicators with
acceptable readings that they may not notice a failed measurement. Both handlers and end
users must be constantly alert to indicators that have not changed color, and to
indicators whose color is suspect.
Handlers and users must also understand procedures for correct use and interpretation
of their chemical indicators. That means reading the instructions that are included with
indicators and familiarizing themselves with manufacturers' recommendations for use.
It is also important to recognize that chemical indicators and chemical integrators are
different. Chemical indicators are designed to detect the presence of a specific
sterilant. Chemical integrators are designed to detect the presence of a specific
sterilant and they also incorporate a time factor. In other words, these products do not
develop a reading upon first contact with the sterilant. Instead, they are designed to
require exposure to the sterilant for a specific period of time before they change color.
Figure 1: Raven's ProChem air removal test.
Another indicator used by healthcare facilities in assessing the quality of their
sterilization process is the biological indicator (BI). BIs contain live bacterial spores
and are designed to measure the sterilization cycle's ability to actually kill spores.
Biological indicators are the only sterilization quality assurance tests that provide this
indication (Figure 2).
There are many types of biological indicators on the market. It is important to follow
manufacturer's instructions for use on the brand that your facility uses. All biological
indicators work in the same basic fashion. The live bacterial spores are subjected to a
routine sterilization cycle. Upon completion of the cycle, the spores are incubated
according to manufacturer's guidelines. If any spores have survived, the indicator will
experience a color change. If all spores have been destroyed, the indicator's color will
remain unchanged. As with chemical indicators, it is important to use biological
indicators in accordance with manufacturer's instructions. Failure to do so may result in
The use of chemical and biological indicator systems can provide sterilizer operators
and product users with some assurances that the sterilization process has been successful.
When used in conjunction with a comprehensive plan for cleaning, inspection, assembly,
packaging, and sterilizer loading, they can help to ensure that the products used in
patient care are as safe as possible.
Natalie Lind manages the Sterile Processing Department at Innovis Health, Fargo,
North Dakota. She also serves as a Sterile Processing consultant and educator throughout
the United States and Canada.