CRM Advantages – Long Term Control Charts

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?

You Can Create Long-Term Control Charts

Establishing long-term control charts of a product’s performance in a Standard Method can enable manufacturers to better identify trends, detect out-of-control events, reduce variation, and facilitate decision-making, ultimately leading to better product quality and customer satisfaction.

For Standard Antimicrobial Methods, a challenging aspect to interpreting a control chart is determining how the inherent variability in Standard Untreated Controls (UTCs) could impact the calculations, or if improper Method performance impacted the results. By including a Certified Treated Test Control in all of your testing, you can gain insight into the performance of the Method, and minimize uncertainty associated with the result. Below is an example of a long term control chart that can be generated.


Occasionally, manufacturers will send samples for testing to multiple laboratories and receive conflicting results. Determining which lab is “correct” can be an expensive and arduous task. Long term control charts including Certified Reference Materials provide context that allow businesses to better compare results across multiple analysts and laboratories, saving a significant amount of time and money following an undesired result that would have been spent on investigations, meetings, and retests.

For laboratories that perform Standard Antimicrobial Methods, control charts can be generated to detect if there are any variations to Method performance between analysts or laboratory locations. Furthermore, the potential impact of proposed Method changes can be evaluated prior to implementation.

On top of all of these benefits, control charts can be utilized to establish the required measurement uncertainty of an ISO 17025 accredited Method, minimizing the need for complex statistics to achieve this.

What are the Additional Benefits?

Standard Controls Can Invalidate Your Testing

Many Standard Antimicrobial Methods have validity criteria requiring the Untreated Control to demonstrate microorganism growth. When the control doesn’t meet this criteria, your test results may be invalidated – leading to frustrating delays and retests. Some antimicrobial methods will additionally have you evaluate a product’s performance by comparing directly to the control. When the control displays antimicrobial performance, or simply doesn’t promote growth, this harms the result of your product.

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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.

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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