A comparison of different sample matrices for evaluating functional sensitivity, imprecision and dilution linearity of the abbott ARCHITECT® i2000® TSH assay

Important performance characteristics for any thyroidstimulating hormone (TSH) assay include lowend sensitivity, precision across a wide dynamic range, and linear specimen dilution. Laboratories often characterize the performance of their TSH assay using many different sample matrices (e.g. native human serum, synthetic buffer, processed human serum, etc.). However, this can lead to possible confusion as the relationships between sample matrix and assay performance are often poorly understood. The purpose of our study was to evaluate the performance of the ARCHITECT i2000 TSH assay using a variety of different sample matrices. Functional sensitivity was found to be essentially equivalent in both hyperthyroid patient sera (0.0035 IU/ml) and TSH affinitystripped (0.0038 IU/ml) sample matrices. Assay imprecision was also independent of sample matrix, with total imprecision less than or equal to5.3% for both synthetic buffer and serum matrices. Similarly, specimens were found to dilute linearly over a wide range in both serum and synthetic buffer matrices. We conclude that the i2000 TSH assay measures TSH similarly in a variety of sample matrices. This is an important design feature for this immunoassay which provides assurance that analytical performance assessed with matrices other than unprocessed human serum are representative of assay performance seen with patient specimens.