Why Commutable Quality Control Materials Are Essential for Reliable Laboratory Performance
How confident are you that your QC materials will behave like real patient samples when reagent lots change?
A large multi‑year study, titled “Commutability Limitations Influence Quality Control Results with Different Reagent Lots” which covered 661reagent lot change events has revealed a crucial insight for clinical laboratories: many QC materials do not respond in the same way as patient samples when new reagent lots are introduced. In more than 40% of events, QC results behaved differently from patient specimens, a clear indicator of non-commutability.
This inconsistency means QC shifts can send mixed messages: sometimes suggesting issues that don’t affect patient results, and other times appearing stable even when patient values are drifting. The findings highlight a simple but powerful truth: the extent to which your QC materials are commutable directly impacts the reliability of your laboratory’s quality assessment.
Randox offers a range of controls manufactured from 100% human serum, specifically designed to mimic patient sample performance across reagent lots and analytical platforms.
What Is Commutability and Why Does It Matter?
Commutability describes how closely a QC or EQA material mirrors the behaviour of real patient samples across different instruments, reagent lots and analytical conditions. When QC materials are commutable, they respond predictably and consistently giving laboratories confidence that their quality system is aligned with clinical reality.
However, many stabilised or processed QC products undergo matrix alterations that affect how they interact with new reagent formulations. These matrix‑related biases are the root cause of non-commutability and can vary significantly between lots, analytes and platforms.
Choosing QC materials with strong commutability minimises these effects and ensures that the changes observed during routine quality checks truly reflect what is happening with patient samples.
Key Insights from the Study
Across 18 QC materials, 661 reagent lot changes, 1483 QC events, 82 analytes and 7 analytical platforms, several important trends emerged:
- Non-commutability Is More Common Than Expected
Over 40% of reagent lot changes showed a disconnect between QC behaviour and patient results, highlighting the importance of evaluating the commutability of control materials - Larger QC Shifts Are Especially Unreliable
When QC values changed by more than 1 SD, more than half of those events did not reflect true patient behaviour. - All Platforms Were Affected
The findings spanned:
– General chemistry
– Immunoassay
– ISE analysers
No platform or QC type consistently matched patient responses, reinforcing the need to select controls with proven commutability.
The Consequences of Poor Commutability
When QC materials are not sufficiently commutable, laboratories are exposed to two risks:
False Alarms
QC shifts appear significant, but patient results remain stable.
This can lead to unnecessary troubleshooting, reagent waste and operational delays.
False Reassurance
QC appears unchanged, but patient values are drifting.
This can mask true analytical bias and compromise clinical decision‑making.
Both scenarios emphasise why the commutability of QC materials is more than a technical detail, it is a patient safety issue.
Why Non-commutability Happens
Matrix modifications such as preservatives, protein adjustments and stabilisers, though essential for shelf life and usability, alter how QC materials interact with different reagent compositions. These interactions are complex and can vary from lot to lot, making non-commutable materials inherently unpredictable.
This is why selecting QC products designed with minimal matrix effects and optimised for commutability is essential for reliable performance.
What Laboratories Should Do
Choose QC materials with strong evidence of commutability
Controls that closely mimic patient samples offer more accurate, clinically aligned performance monitoring, especially across reagent lot changes.
Review QC behaviour across platforms and manufacturers
Materials with demonstrated consistency provide greater confidence over time.
Work with suppliers who prioritise commutability
Transparent information, lot‑specific data and materials engineered for patient‑like behaviour reduce the risk of misleading QC shifts.
Conclusion: Choosing Commutable QC Materials Is Key to Reliable Results
This landmark research shows that many conventional QC materials fail to mimic patient behaviour when reagent lots change, creating inconsistent or misleading quality signals. As laboratories continue to prioritise accuracy, efficiency and patient safety, the importance of selecting high‑quality, commutable QC materials has never been clearer.
By choosing control materials engineered for strong commutability, such as Randox, laboratories can improve the reliability of their quality systems, reduce unnecessary investigations and strengthen confidence in every result they report.
Learn more about our solutions here.
Miller, W.G., Erek, A., Cunningham, T.D., Oladipo, O., Scott, M.G., & Johnson, R.E. (2011). Commutability Limitations Influence Quality Control Results with Different Reagent Lots. Clinical Chemistry, 57(1), 76–83