Lot to Lot Correlations

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Lot to lot correlations are common in today’s clinical laboratories. As explained in the recent CAP today article, “Differences between reagents and testing systems are known to contribute to test result variability, making crossover studies necessary when using new reagents or implementing new testing systems.”[1] Regulatory and accreditation standards require the lab to evaluate each new lot of reagent.

Even though reagent performance is validated by the manufacturer before release, the laboratory needs to verify that the new reagent lot meets the laboratory’s clinical performance needs. Possible causes of a change in performance with a new reagent lot include:

  • Changes in reagent component materials
  • Instability of a component in a reagent
  • Reagents compromised in transportation or storage
  • Incorrect calibration of the new reagent lot

This testing is important to assure the quality of laboratory results [2]

How the lot to lot evaluation is done varies widely among clinical laboratories.   Reagent lot to lot variation can affect the QC results, patient results or both. Therefore, it is important to include in the lot to lot evaluation samples most like your patients. If using QC and/or proficiency material only, it may appear as if no difference exists between lots due to the matrix of the prepared material.

The number of samples tested between laboratories also varies. “There are no universally agreed upon acceptance or rejection criteria for new reagent lots. It is up to the laboratory management to determine what is acceptable.”[3]

Though it has increased work for the laboratory, lot to lot evaluation is necessary to prevent use of “suboptimal” reagent lots. The process of lot to lot evaluation can be easier by planning ahead and will enable a laboratory to report test results with confidence.


[1] Tricot, Mark X., PhD. “Q and A.” CAP TODAY. College of American Pathologists, Dec. 2007. Web. 15 May 2017.

[2] EP26-A: User Evaluation of Between-Reagent Lot Variation; Approved Guideline. Clinical and Laboratory Standards Institute. September 2013

[3]Algeciras-Schimnich, Alicia, PhD. “Tackling Reagent Lot-to-Lot Verification in the Clinical Laboratory.” Clinical Laboratory News July 1 (2014): n. pag. Web. 15 May 2017.