How to be certain that your washer works well in your facility and ensure a margin of safety for your patients

Washer-disinfectors have two functions: washing the instruments to get them repeatably and reliably clean and free of foreign materials (bioburden, residual soil, detergents) and disinfection so that the instruments are safer to handle on the clean side than in decontam. Both are essential for efficacious and safe processing of the instruments.

How do you know that the machine you have does these things? For cleaning, you can use cleaning tests. For disinfection, you check the high-temperature rinse phase parameters. Okay, done? No.

Good vs. bad cleaning

There is an invisible line between good and bad cleaning results that differs for each instrument processed. This line may be represented by the challenge your cleaning indicator provides to the process, or the instrument may provide an easier or more difficult challenge. If the instrument provides an easier challenge, your cleaning indicator tests provide a safety margin. If the instrument’s challenge is greater than the cleaning indicator, there is no safety margin, and your indicator is giving you a false sense of security.

Another issue is that washer-disinfectors tend not to be qualified with rigorous testing after installation. Typically, they are tested against the same indicators that you use. This results in them essentially being treated as a black (okay, stainless steel) box.

If the cycles are validated at the factory, you have no certainty of how well they process the instruments in the unique conditions of your facility (water chemistry, water pressure, water temperature, detergent dosing, detergent type, specific rack used, condition of that, etc.). If the testing that is done at installation uses the same indicator you use on a routine basis, with the acceptance criterion being no visible soil after cleaning, you don’t know how much safety margin you have.

No standard means no general comparison

Cleaning indicators have no standard against which resistance to a cleaning process can be determined. This means that each indicator may and probably will present a different challenge to each different washer’s processes. Because of this, a general comparison cannot be made of which is more difficult to clean because of this. You have to test each candidate indicator in your washer to see which is the most resistant in your unique situation. And then you must pick the one that is hardest to clean, since we live in a world where “worst case” is the only criterion that matters.

A proper, rigorous qualification program for your washers would test every cycle program and every rack with appropriate cleaning tests that are hard to clean so as to get to cycle parameters that will clean the easiest and hardest challenges your facility has. But how?

This does not mean that you smear test soil onto and into instruments, let it dry, and try to clean them. That is the job of the washer-disinfector manufacturer, who uses testing as defined in the AAMI/ISO 15883 standards to show that the washer can clean per the requirements of those standards. But it does not show that this performance can be achieved at your site. You have to do that if you want to be sure of your cleaning results.

So, again, how?

Process challenge devices (PCDs)

A number of manufacturers of cleaning indicators have PCDs that allow their indicators to present a specific challenge to the process. These can be PCDs that mimic a lumen challenge or hard-to-reach portions of instruments. Some manufacturers provide indicators with different levels of challenge: one for routine use and another for qualification. In any of these cases, if the indicator is not visibly clean of all residues, the cycle failed the test. Is the indicator clean if all residues are visibly absent? Maybe.

If using a real biological challenge like blood, you can check for invisible soil residue using adenosine triphosphate (ATP), or preferably, protein testing. The United Kingdom standard HTM 0101 part D requires no more than 5 µg of protein per instrument side remain after washing and that the washer-disinfector’s cleaning performance be validated to reach that (low) level of residual protein.

In contrast, the US Food and Drug Administration (FDA) requires that instruments be cleaned to leave no more than 6.4 µg/cm2 of protein per instrument in total. If you have an instrument with a lot of surface area like an endoscope, you can meet the US criteria while failing the UK criteria miserably. Can your washer achieve the US-required level of soil removal? The UK-required level? Maybe yes, maybe no. You don’t know until you test.

Running your tests

What’s the starting point for this extended qualification? First, find an indicator that can be tested for residual protein and comes in configurations for normal and lumen use.

Place indicators throughout the load or empty racks to measure cleaning capability throughout the washer chamber. If you are testing lumen configurations, connect the lumen PCDs to the connections on the rack nearest and farthest from the connection from the washer to the rack. Since flow to the lumens will generally be affected by how many lumens are connected, the rack should have lumened devices connected to all connections to provide the worst-case conditions. This is because the same flow to the rack will be directed to all of the connections, decreasing the available pressure and flow to each connection.

Observe and record the state of the indicators after washing. Test the processed indicators that show no residual soil for residual protein. If the result is <5 µg protein per instrument side, you have a process that goes above and beyond the US national requirements and are doing your patients an excellent service.

If there is visible residual soil, your cycle parameters are inadequate for the cleaning challenge. If your residual protein level is above 5 µg per instrument side, calculate the approximate number of cm2 in the instrument’s surface area and the surface area of the cleaning challenge on the indicator. Divide the residual protein value by the area of the cleaning challenge on the indicator. This is a proxy for the residual protein per cm2 on the instrument. If the value is less than 6.4 µg/cm2, you are in compliance with the FDA’s requirements.

But what if you aren’t in compliance and above both acceptance levels? You have to adjust the cycle parameters to get cleaning results that do comply.

Checking settings and calculations

How? First and foremost, make sure that the detergent dosing is calibrated and appropriate for your water chemistry. Many detergent manufacturers can tell you what that dose should be based upon the conductivity/total dissolved solids in the utility water used in the wash phases. If they don’t tell you this, it may be time to look for a new vendor.

If the soil on the indicator is blood-based and the original color remains in the soil, make certain that the prewash uses cold water and extend it long enough to remove the hemoglobin.

If the blood color is gone, but residual protein is present, you must ensure that the enzyme detergent is used at its highest possible use temperature (see its manufacturer’s instructions for use [IFU], but typically 122°F/50°C) and is given enough time to work. Consider extending the enzyme wash phase by one minute. If there is still residual soil, extend by another minute. Continue this until the indicator is clean.

If residual visible soil remains but the protein levels are acceptable, your neutral detergent isn’t doing its job. You may need to increase its temperature (see its manufacturer’s IFU, but typically 149°F/65°C) and possibly extend the neutral wash phase time.

These issues are critical to getting a safety margin in the cleaning process. I am happy to discuss this subject and look forward to your call!