In the field of sterilization technology, it is well known that visual inspection alone is not always sufficient to verify cleaning results. Several standards and guidelines, including the ISO for washer-disinfectors, therefore emphasize the importance of objective cleaning verification as a complement to visual inspection. Protein tests have now become an established tool for this purpose.
Why do we measure protein?
Protein is not only commonly found in blood, tissue, and body fluids. It also has a property that makes it particularly interesting in the field of sterilization technology—it can be very difficult to remove from instrument surfaces.
When protein dries, it can adhere tightly to surfaces and form residues that require an effective cleaning process to remove. This is especially true for instruments with joints, seams, grooves, and other hard-to-reach areas.
For this reason, protein is often regarded as a “worst-case” indicator of cleaning quality. If the cleaning process is able to remove dried-on protein residues, there is good reason to believe that other organic contaminants have also been effectively removed.
Different rapid tests for different needs
There are many different types of protein tests available to check cleaning results. What they all have in common is that they provide quick results and are relatively easy to use. Many people therefore believe that it doesn’t matter which one is used and that price is the deciding factor.
However, the difference between the methods may be greater than one might think. Some tests indicate whether protein is present or not, while others can measure the actual amount of protein and be used for trend analysis, comparisons, and validation of cleaning processes.
The choice of method should therefore not be based on which test is the cheapest, but on what information the organization needs to ensure and monitor the cleaning process.
Protein tests in sterilization technology can be broadly divided into three levels:
- Qualitative tests
provide a yes/no answer as to whether protein residues can be detected or not. - Semi-quantitative tests
provide a color-coded indication of the extent of protein residues and are well suited for regular process monitoring. - Quantitative tests
are colorimetric tests that measure the actual amount of protein and provide a numerical result that can be used for validation, documentation, and comparison between different processes.
The table below compares some common protein tests used in sterilization technology. The differences primarily concern the type of information the test provides—ranging from qualitative control to quantitative measurement for trend analysis and validation.
| Product | Method | Result type | Typical uses |
|---|---|---|---|
| RESI-TEST™ | Immediate color reaction without incubation | Qualitative | Verification of protein residues after cleaning. |
| Clean-Trace™ Surface Protein High Sensitivity | RT or incubation-based color-scale reaction | Semi-quantitative | Same as above + for more process control. |
| Chemdye® PRO1 MICRO | Instrument-based protein analysis (incubation with color scale) | Quantitative | Same as above + validation , trend analysis, and documented cleaning verification. |
| Chemdye® PRO1 ENDO | Instrument-based protein analysis for the lumen | Quantitative | Same as above + inspection of endoscopes and instruments with internal channels. |
Summary
Protein tests make it possible to detect biological residues that cannot be identified through visual inspection alone. Because protein can be difficult to remove from instrument surfaces, it is often used as a “worst-case” indicator of cleaning quality.
Whether the goal is a quick routine check, regular process monitoring, or documented validation, there are methods available today that can be tailored to the needs of your organization.
The right test is therefore not about choosingthe cheapest ormost advanced method, but about choosing the method that provides the information needed to ensure a controlled and reproducible cleaning process.
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