Evaluation of the CLSI EP26-A protocol for detection of reagent lot-to-lot differences.
BACKGROUND
Verification of new reagent lots is a required laboratory task. The Clinical and Laboratory Standards Institute (CLSI) EP26-A guideline provides a lot-to-lot verification protocol to detect significant changes in test performance. The aim of this study was to compare the performance of EP26-A with our laboratory reagent lot verification protocol.


METHODS
Prospective evaluations for two reagent lots each for thyroid stimulating hormone (TSH), thyroglobulin (Tg), thyroxine (T4), triiodothyronine (T3), free triiodothyronine (fT3), and thyroid peroxidase antibody (TPOAb) were performed. The laboratory's lot verification process included evaluation of 20 patient samples with the current and new lots and acceptability based on a predefined criteria. For EP26-A, method imprecision data and critical differences based on previously defined lot-to-lot consistency goals were used to define sample size requirements and rejection limits.


RESULTS
EP26-A required the following number of samples: 23 for TSH, 17 for Tg, 33 for T4, 31 for T3, 48 for fT3, and 1 for TPOAb. Our current protocol and EP26-A were in agreement in 9 of the 12 (75%) paired verifications. Of the 3 discrepant verifications, Tg and TSH reagent lots were rejected by EP26-A due to significant differences at medical decision points; whereas TPOAb was rejected by the current laboratory protocol.


CONCLUSIONS
The EP26-A protocol arrived at the same conclusions as our protocol in 75% of the evaluations and required more samples for 4 of the 6 analytes tested. Challenges associated with determining rejection limits and the need for increased sample sizes may be critical factors that limit the utility of EP26-A.
Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, United States.
Brooke M
BM
Katzman
Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, United States.
Karl M
KM
Ness
Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, United States. Electronic address: algecirasschimnich.alicia@mayo.edu.
Alicia
A
Algeciras-Schimnich
D000046:Academic Medical Centers; D001323:Autoantibodies / Q000097:blood*; D001324:Autoantigens; D017408:Guidelines as Topic; D006801:Humans; D007118:Immunoassay / Q000592:standards; D007202:Indicators and Reagents / Q000737:chemistry* / Q000592:standards; D007390:International Agencies; D007453:Iodide Peroxidase / Q000037:antagonists & inhibitors*; D033862:Iron-Binding Proteins / Q000037:antagonists & inhibitors*; D008910:Minnesota; D011786:Quality Control; D012044:Regression Analysis; D015203:Reproducibility of Results; D012995:Solubility; D013954:Thyroglobulin / Q000097:blood*; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood* / Q000737:chemistry
D001323:Autoantibodies; D001324:Autoantigens; D007202:Indicators and Reagents; D033862:Iron-Binding Proteins; D014284:Triiodothyronine; D013972:Thyrotropin; D013954:Thyroglobulin; C056658:TPO protein, human; D007453:Iodide Peroxidase; D013974:Thyroxine
CLSI EP26-A; Immunoassay; Lot verification; Reagent lot variability