A-067 Evaluation of the Analytical Performance of Anti Thyroid Peroxidase II Assay on the Atellica CI Analyzer

Abstract Background Thyroid peroxidase (TPO) is a membrane-bound glycosylated heme-containing protein found in the apical membrane of thyroid follicular cells. TPO catalyzes iodination of tyrosyl groups in thyroglobulin resulting in thyroid hormones, T3 and T4. Autoimmune thyroid disease is characterized by the presence of autoantibodies against TPO. Anti TPO antibody levels are increased in greater than 90% of patients with active autoimmune thyroiditis. Anti TPO antibodies activate, complement, and are thought to be significantly involved in thyroid dysfunction and the pathogenesis of hypothyroidism. In autoimmune thyroid disease, anti TPO antibodies are present in nearly all patients with Hashimoto’s thyroiditis and in greater than 70% of patients with Graves’ disease. Levels of anti TPO antibodies are increased in 5%–9% women with postpartum thyroiditis, 50% of whom do not develop thyroid dysfunction. The measurement of anti TPO antibodies can be useful in diagnosing maternal Graves’ disease or Hashimoto’s thyroiditis. This study evaluated the analytical performance of the Atellica IM Anti Thyroid Peroxidase II (aTPOII) assay on the Atellica CI Analyzer. The Atellica CI Analyzer is an automated, mid-throughput integrated chemistry and immunoassay analyzer employing both Atellica CH and Atellica IM assays Methods The Atellica CI analyzer uses the same reagents and calibrators as the Atellica IM analyzer. Precision studies followed CLSI EP05-A3 using native human serum and quality control samples. For repeatability and within-lab precision, samples were tested in duplicate in 2 runs/day for 20 days (n=80) using one reagent lot and two analyzers. Reproducibility samples were assayed in five replicates/run, 1 run/day for 5 days using three lots on three analyzers (n=225 measurements/sample). Method comparison (MC) studies used human serum samples according to CLSI EP09c-ED3 to compare the aTPOII assay on the Atellica IM and the Atellica CI analyzers. Samples were assayed in singlicate on one of two Atellica CI Analyzers using three reagent lots. Limits of Blank, Detection, and Quantitation (LoB, LoD, and LoQ) were tested in accordance with CLSI EP17-A2. For LoB and LoD, each of four samples was assayed in twelve replicates/run, 1 run/day for 5 days (n=60 measurements/sample per lot), for three reagent lots, each run on one of three analyzers. For LoQ (lowest amount at CV<20.0%), samples were assayed in duplicate in 2 runs/day (minimum of 2 hours between runs) for 20 days (n=80/lot) with three reagent lots on two analyzers/lot. Linearity studies tested 19 levels of mixed high, intermediate, and low samples (n=4/level) over 3 days and three lots. Results Repeatability coefficients of variation (CV) were 2.4–5.3% and within lab CVs 3.9–11.4% for concentrations 15.2–378.9 IU/mL. Reproducibility CVs were 3.9–8.0% at 13.8–343.0 IU/mL. Representative Passing-Bablok regression results for MC between Atellica IM and Atellica CI analyzer yielded a slope of 1.01 and intercept of 0.3 IU/mL (sample interval: 7.2–368.4 IU/mL). LoB, LoD, and LoQ were 3.0, 6.6 and 6.6 IU/mL. The assay was linear from 6.6–400.0 IU/mL. Conclusion Evaluation of the Atellica IM aTPOII assay on the Atellica CI Analyzer demonstrated acceptable analytical performance and acceptable concordance compared to the Atellica IM Analyzer.