Laboratory standards and regulations require the verification of reagent lot performance prior to use, as each new reagent lot could potentially affect quality control material and/or a patient sample.
The July article, "Tackling Reagent Lot-to-Lot Verification," in Clinical Laboratory News, written by Alicia Algeciras-Schimnich, Ph.D., associate professor of Mayo Clinic Laboratory Medicine and Pathology and director of Mayo's Clinical Immunoassay Laboratory, discusses the multiple factors that can affect performance of a new reagent lot, including changes in a critical reagent material or in stability of the reagents, reagent damage during transportation or storage, or incorrect calibration.
According to Dr. Algeciras-Schimnich, clinical laboratory practices for lot-to-lot evaluation vary widely - from testing as few as three to four samples to as many as 20 to 40 samples with each new reagent lot. Additionally, different samples are tested, such as the QC material supplied by reagent vendors, third party QC material, in-house QC material, or patient samples.
While there has not been a standardized protocol or guideline to date for lot-to-lot reagent verification, the Clinical and Laboratory Standards Institute (CLSI) recently published the document, "EP26-A - User Evaluation of Between-Reagent Lot Verification," to offer laboratories a protocol for patient sample testing.
Dr. Algeciras-Schimnich describes the two phases of the protocol:
- Gathering data to establish a number of parameters to determine the number of samples to be tested and the rejection limit necessary to assure the critical difference is detected. These parameters include:
- Maximum difference between the two reagents lots that is acceptable without having an adverse clinical impact
- Laboratory-observed method imprecision
- Desired statistical power for detecting significant lot-to-lot changes
- Verification of the new reagent lot by testing the determined number of samples with both lots of reagents, calculating the average concentration differences, and analyzing acceptability of the new lot based on the rejection limit established.
According to Dr. Algeciras-Schimnich, while lot-to-lot verification is necessary, it is also critical for laboratories to plan ahead and allow time for performing repeat evaluations if needed.
Read the full article in the July issue of Clinical Laboratory News.