Laboratory Quality Control

Using Third Party Quality Controls to Improve Laboratory Performance

Using Third Party Quality Controls to Improve Laboratory PerformanceAnyone working in a laboratory will understand the importance of quality control. QC is the process used to detect errors in order to ensure reliability and accuracy of patient test results. Without QC laboratory errors could go unnoticed, potentially resulting in misdiagnosis and inappropriate or delayed treatment, all of which could be life-threatening to the patient.

When running internal QC laboratories need to have confidence in the accuracy of the results produced. Only by using third party quality controls can they truly be assured of this. So what is the difference between a third party control and a control from an instrument or reagent manufacturer, and why should laboratories be using third party controls?

Third party is the term used to describe a control that has not been designed or optimised for use with a specific test or system. As such it will better mirror the performance of patient samples and provide an unbiased, independent assessment of analytical performance.

Many instrument and reagent manufacturers provide dedicated quality controls for use with their own reagents and analysers. Optimised for use with these specific assays or systems, these controls often mask weaknesses and therefore are increasingly considered less effective compared to third party controls.

This is a fact that is recognised by regulatory bodies and standards around the world, and this is corroborated in ISO15189. The Clinical and Laboratory Standards Institute (CLSI) sums it up nicely in the following statement:

“Quality control materials should be different from the calibrator materials to ensure that the QC procedure provides an independent assessment of the measurement procedure’s performance in its entirety, including the procedure for calibration of the measurement.”

Third Party Controls

True third party controls are manufactured independently meaning they give totally unbiased results.

The leading third party control manufacturers assign target values using data from thousands of independent laboratories – genuinely independent, multi-method, and multi-analyser data. The target values are, as a result, more accurate and reliable.

Some third party controls offer extended shelf life of up to four years. This enables long term QC monitoring and the detection of shifts upon change of reagent batch. This can help laboratories save time and money due to fewer lot crossovers.

Versus:

Instrument/Reagent Manufacturers Controls

Some manufacturers use the same raw material to make both controls and calibrators, making the controls less sensitive to performance changes.

It is not uncommon for instrument/reagent manufacturers to assign their QC values using only a limited number of results generated on their own instruments, using their own reagents and calibrators. This can result in perceived accuracy, unrealistic wide ranges and batch to batch variability.

Laboratories using an ‘in-kit’ control will receive a new lot of QC with each new batch of reagents meaning they are constantly changing lot number and do not have the benefit of long term QC monitoring.

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The following real life laboratory case studies highlight the importance of third party controls and how they can be used to help identify instrument, reagent and procedural errors.  If errors remain undetected this could result in the reporting of incorrect patient results, potential misdiagnosis, causing delayed treatment and possibly even the death of the patient.

Case Study 1

A laboratory in England contacted Randox Technical Support , reporting higher than range QC results for Thyroglobulin. When using third party controls (Acusera Immunoassay Premium Plus control) the results were four times higher on their main analyser compared to other systems.  However, when they ran the instrument manufacturer’s control alongside the third party control it did not show the same problem.

After reviewing the EQA data, the Technical Support team confirmed there was a significant difference in results between the instruments, and set about helping the laboratory troubleshoot.  After an exhaustive review of procedures and processes, the customer contacted the instrument manufacturer, who advised of a positive bias with several batches of reagent, including the batch the laboratory was using.

Conclusion: By using a third party control the laboratory was able to detect a shift in results after changing reagent batch that the instrument manufacturer’s control did not.

Case Study 2

Randox Technical Support team were contacted by a laboratory which was experiencing problems with low recovery of the Acusera (Randox) third party control they were using for ALT. The instrument manufacturer had advised the laboratory that it was a control problem and recommended that if they used a control from another manufacturer they would not observe the problem. Randox investigated the problem and demonstrated that patient results were also being wrongly reported low. When Randox ran the test using the control recommended by the instrument manufacturer it failed to highlight the problem, leading the Randox Technical support team to the conclusion that the matrix of the recommended control must be different to a patient matrix.

The instrument manufacturer recommended a wash stage to the customer which eliminated the carryover interference which was causing the low ALT results.

Conclusion: The customer overcame this problem by programming in an extra wash cycle. However, had the lab used the QC recommended by the instrument manufacturer they would never have identified that they had a problem and would have continued to report inaccurate patient results leading to possible patient misdiagnosis. A good Quality Control only works effectively if it has a similar matrix to the sample type being tested.

Case Study 3

A laboratory, using Randox Immunoassay Premium Plus control, reported that their QC results for Sex Hormone Binding Globulin (SHBG) were much higher than the target values provided. When the lab ran the reagent manufacturer’s control the results were within the given ranges.

After reviewing the reagent kit insert the Support team noticed that the instrument the laboratory was using automatically diluted patient samples but not controls. Lab staff were unaware of this and had not been diluting the controls.

Conclusion: By using third party controls, a procedural error was identified that the reagent manufacturer’s control was masking. Good laboratory practice is to run quality control materials the same way as a patient sample and, going forward, laboratory staff amended their procedures accordingly.

For more information on the benefits of third party controls visit http://www.randox.com/laboratory-quality-control.php

By: Steven Jordan, Global Business Manager, Randox QC

 

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