CRM Advantages – Avoid Negative Impact of In-House Controls

What are Certified Reference Materials for Antimicrobial Testing?

Situ Biosciences’ Certified Reference Materials (CRMs) are quality standards designed to be utilized as test controls in Standard Antimicrobial Methods. Situ Biosciences Certified Treated Test Controls are designed to achieve significant antimicrobial performance in a Method, and Certified Untreated Test Controls are designed to have an extremely poor antimicrobial performance. The desired outcome of a given Method determines how each control is expected to perform.

These values have been determined through the relevant Standard Method performance in Situ Biosciences’ facilities, which are accredited to ISO/IEC 17025, ISO 17034, and Good Laboratory Practices. For answers to our most frequently asked questions, click here.


Why Should I Use a Certified Reference Material? 

In-House Controls Can Invalidate Your Testing

Many Standard Antimicrobial Methods have validity criteria requiring an untreated control to demonstrate microorganism growth, which labs traditionally use an In-House Control to satisfy. When the In-House Control doesn’t meet this criteria, your test results may be invalidated – leading to frustrating delays and retesting.

For example: AATCC TM100 section 10.4 includes that for a valid test there should be “a significant (≥ 1 log) increase in the numbers of bacteria recovered from the inoculated viability control specimen swatches incubated for the specified contact time over the numbers of bacteria recovered from the inoculated viability specimen swatches at “0” contact time (immediately after inoculation).”

As reflected in the chart to the right, In-House Controls (IHCs) have undesired antimicrobial performance in up to 1 out of 4 tests.* Certified Reference Materials are designed to eliminate this unpredictable result and validate your test performance.

In-House Controls Can Hinder your Results

Some Antimicrobial Methods including ISO 22196 will additionally evaluate a product’s performance by comparing the amount of microorganisms present on the product against the untreated control.

This is commonly found in the form of a percent reduction, where  % Reduction = (Control Count – Sample Count) / Control Count.

When the In-House Control displays antimicrobial performance, or simply doesn’t promote growth, this directly impacts the result of your product. In the chart below, we’ve utilized internal data to illuminate the potential difference in results that can be achieved by utilizing Untreated Certified Reference Materials (CRM) instead of the In-House Control (IHC).

During the development and homogeneity testing of our ISO 22196 CRM products, we found that utilizing the Untreated CRM instead of the IHC provides a consistent, optimized comparison that can improve the final results of a product by up to 1 log. This may be critical for the product, as the industry generally defines a significant, repeatable performance as a reduction of at least 99% (2 logs)**. 

What are the Additional Benefits?

You Can Create Long-Term Control Charts

CRMs will provide insight into the performance of the product, allowing you to create long term control charts to monitor the performance of your products. This insight will allow a customer to make strategic decisions when implementing any design changes to that product or any future products that are developed.

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Gain and Maintain ISO 17025 Accreditation

Click on a topic below to learn how Situ Biosciences’ Certified Reference Materials can be used to satisfy ISO 17025 requirements.

*Charts generated are based upon data from a traditional control’s performance in relevant Antimicrobial Methods. For more information, contact Situ Biosciences.   

Personnel Training - - ISO 17025 § 6.2.5

Training personnel in Standard Antimicrobial Methods can be challenging due to the inherent variability associated with all microbiological testing, especially when it comes to analyzing the results obtained by trainees.


Certified Test Controls have accounted for this variability to provide a known result; allowing reviewers to more easily evaluate if the trainee obtained the proper result for the sample under test.

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Metrological Traceability - - ISO 17025 § 6.5.3

Certified Test Controls directly fulfill this section, and may eventually be required.


ISO 17025 states the laboratory shall demonstrate metrological traceability to an appropriate reference. The certified values of our Certified Reference Materials fulfills this requirement.


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Selection, Verification, and Validation of Methods - - ISO 17025 § 7.2

These vital requirements can be fulfilled by simply including Certified Reference Materials in their testing.


By consistently achieving the Certified Values at both extremes of a method, laboratories inherently verify their performance of a method, and evaluate if any modifications may have an impact to the ability to accomplish the purpose of the method.

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Measurement Uncertainty - - ISO 17025 § 7.6

Due to the inherent variability present in microbiological testing, complex statistical calculations are typically necessary to fulfill this requirement.


Certified Reference Materials simplify this process by providing an expected, consistent result. This consistency allows laboratories to properly evaluate the variance between replicates and samples over the long term, minimizing the amount of statistics that are needed to support the evaluation of the measurement uncertainty.

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Ensuring Validity of Results - - ISO 17025 § 7.7

Fulfillment of this requirement has never been more straight-forward!


By utilizing Certified Reference Materials in your antimicrobial testing, and achieving the Certified Values, your performance of the method can be inherently validated. Situ Biosciences can additionally provide blind samples of our Test Controls to further bolster your method performance validation.

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Actions to address risks and opportunities - - ISO 17025 § 8.5

Utilization of ISO 17034 Certified Test Controls shows that your laboratory actively seeks out opportunities to assist in achieving the purpose and objectives of the laboratory.


When included in your antimicrobial testing, they will provide insight that will allow laboratories to prevent, or reduce, undesired impacts and potential failures in the laboratory activities.

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Improvement - - ISO 17025 § 8.6

Utilizing Certified Test Controls in your antimicrobial testing communicates that your laboratory actively identifies opportunities for improvement and implements them into your procedures.


In addition to this, utilizing our Certified Test Controls in your internal processes such as proficiency testing will provide insight into other potential opportunities for improvement; allowing you to continuously improve and satisfy this requirement long term.

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