Lot to Lot Reagent Verification: A Practical Guide on How to Do It?

Background: Lot to Lot reagent verification (LTLV) is done to check suitability of new lot of reagents for use. Except EP26, 2nd edition, 2022 by Clinical and Laboratory standards Institute, hardly any guidance document is available for LTLV. In present study, authors guide on how to perform LTLV using In-house & EP26 protocol with examples of Glucose, Aspartate Amino Transferase (AST) & Cholesterol using Quality control material and Patient Samples. The difficulties using EP26 protocol for LTLV have also been stated.Methods: For In-house protocol,15 patient samples were assayed using current & candidate lot of reagents for Glucose, AST and Cholesterol. Acceptance Criteria were predetermined to verify the suitability of candidate lot. MedCalc software, current version 23 was used for statistical calculations. For EP26 protocol, in stage1, Total Allowable Error (TEa), Critical difference, Sr (within-run imprecision) & SWRL (within reagent imprecision) & Statistical power of 0.8 were determined. In stage 2, number of patient samples needed to be assayed for LTLV was determined using Appendix A in EP26 & Rejection Limit (RL) was derived. Absolute Mean Difference was calculated and verified to be less than RL.Results: For In house protocol, all the predetermined Acceptance criteria were met by the candidate lot of reagents. For EP26 protocol, Absolute Mean difference between the results obtained in current and candidate lot was less than the determined RL.Conclusion: Laboratories Can use Inhouse protocol or EP26 protocol with its inherent difficulties to perform LTLV using guidance provided in this article.