What is the commutability of External Quality Assurance materials ?

Commutability refers to the ability of a material to behave similarly to patient samples when subjected to a specific laboratory test or measurement procedure. In the context of External Quality Assurance (EQA) materials, commutability is a critical characteristic. EQA programs involve external organizations sending samples to clinical laboratories to assess their testing performance. These samples should mimic patient samples as closely as possible to ensure accurate evaluation of a laboratory’s testing accuracy and precision.

Here’s how commutability of EQA materials is important and how it’s assessed:

Importance of Commutability in EQA Materials:

1. Accurate Assessment: The primary purpose of EQA is to evaluate the accuracy and reliability of a laboratory’s testing methods. For this assessment to be meaningful, the EQA materials must behave similarly to patient samples.
2. Real-World Performance: Commutable EQA materials provide insight into how well a laboratory’s methods perform on samples that closely resemble those encountered in actual patient testing.
3. Effective Quality Control: Commutable EQA materials help laboratories identify and correct any issues with their testing procedures and prevent potential misdiagnoses or incorrect treatment decisions

Assessment of Commutability:

1. Method Comparison Studies: Commutability is often assessed through method comparison studies. These studies involve comparing the EQA material’s results obtained from different testing methods (including the laboratory’s routine method) to assess how closely the EQA material’s behaviour aligns with that of patient samples.
2. Reference Materials: Reference materials that have been standardized and widely accepted as accurate are often used to assess commutability. These materials are traceable to an established reference system.
3. Peer Comparison: Laboratories participating in EQA programs compare their results with those of other laboratories using the same EQA materials. If laboratories’ results for the EQA materials are similar, it suggests commutability.
4. Matrix and Analyte Compatibility: EQA materials should have a matrix (composition and properties) that closely resembles patient samples for the specific analyte being tested. This ensures the method’s performance on the EQA material reflects its performance on patients’ samples.
5. Data Analysis: Statistical analysis of EQA results can help identify discrepancies that might indicate lack of commutability. If laboratories consistently obtain different results for EQA materials compared to their routine samples, it suggests potential issues.

In summary, commutability is crucial for the effectiveness of External Quality Assurance programs. Commutable EQA materials ensure that the evaluation accurately reflects a laboratory’s real-world testing performance. Assessing commutability involves method comparison studies, using reference materials, peer comparisons, and ensuring matrix and analyte compatibility.

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About the author

Dr. Sambhu Chakraborty is a distinguished consultant in quality accreditation for laboratories and hospitals. With a leadership portfolio that includes directorial roles in two laboratory organizations and a consulting firm, as well as chairmanship in a prominent laboratory organization, Dr. Chakraborty is a respected voice in the field. For further engagement or inquiries, Dr. Chakraborty can be contacted through email at director@iaqmconsultants.com and info@sambhuchakraborty.com. Additional resourcesand contact information are available on his websites, https://www.quality-pathshala.com and https://www.sambhuchakraborty.com, or via WhatsApp at +919830051583