Evaluation of the Technicon Immuno 1 Free Thyroxine Assay

Bock, Jay L.; Morris, Deborah L.; Cheng, Jiqi; Ehresman, David J.

doi:10.1093/ajcp/105.5.583

Cited by 2 publications

(1 citation statement)

References 14 publications

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“…The recent generation of automated immunoassay platforms has enabled important improvements in precision for thyroid tests (1)(2)(3). With increasing precision, the interpretation of thyroid hormone tests can be better standardized.…”

Section: Introductionmentioning

confidence: 99%

Comparative Multicentre Study of a Panel of Thyroid Tests Using Different Automated Immunoassay Platforms and Specimens at High Risk of Antibody Interference

Martel

Després²,

Ahnadi³

et al. 2000

CCLM

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The introduction of automation for immunoassays in recent years has brought about important and evident improvements in assay precision. Increasing standardization and comparability between platforms should enable the development of clinical guidelines and diagnostic algorithms for appropriate clinical decision making. A continuing source of variation between different automated immunoassay platforms is the sporadic effect of interfering antibodies or substances, thus causing aberrant results not supporting the patient's clinical status. The aim of this study was to describe current thyroid panel variation between automated immunoassay platforms including population specimens at risk of antibody interference. A multisite design with laboratories in three different countries using four different automated immunoassay platforms (Roche-Boehringer Mannheim Elecsys (Italy), Roche-Boehringer Mannheim ES300 (Wales), Bayer Immuno 1 and the Bayer ACS:180 evaluated the thyroid panel of thyrotropin (TSH), triiodothyromine (T3), free thyroxine (FT4) and free triiodothyronine (FT3). A common set of 158 randomly selected patient samples of non-thyroid and thyroid disorders, with and without treatment, was tested. Included were 62 patient samples at risk for endogenous antibody interference with high antimicrosomal antibody, anti-TSH receptor antibody and increased rheumatoid factor sub-populations. Across all controls and between platforms, precision measurements were comparable and varied between 0.7% and 12.8% for TSH, 2.8% and 13% for FT4, 1.8% and 10.5% for FT3 and 3.1% and 16% for T3 assay. Acceptable correlation and reproducibility were found between the three Bayer Immuno 1 platforms at each country's site with all four thyroid panel assays demonstrating r-values of 0.989 to 1.000 and slopes of 0.915 to 1.078. Comparisons between the different platforms showed acceptable correlation for all thyroid panel assays. Specimens containing rheumatoid factor were associated with a significantly increased variation between systems for the FT4 and FT3 assays (p < 0.01). This effect did not appear to be selective for a given platform. For specimens with raised autoimmune antibodies and therefore at risk of assay antibody interference, no variation could be observed between the platforms.

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Section: Introductionmentioning

confidence: 99%

Comparative Multicentre Study of a Panel of Thyroid Tests Using Different Automated Immunoassay Platforms and Specimens at High Risk of Antibody Interference

Martel

Després²,

Ahnadi³

et al. 2000

CCLM

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Accuracy of Free Thyroxine Measurements Across Natural Ranges of Thyroxine Binding to Serum Proteins

Wang¹,

Nelson²,

Weiss³

et al. 2000

Thyroid

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Systemic inaccuracies, proportional to the concentrations of serum proteins and the thyroxine (T4) they carry, have been reported in direct free T4 immunoassays. However, analytical recoveries of free T4 have not been carefully examined in most current methods, and they have not previously been examined across the pathophysiological range of serum T4 binding. In the present study we investigated ranges of serum T4 binding using free and total T4 measurements from 1359 individuals. Carefully characterized, gravimetrically calibrated, serum-based free T4 test solutions were then prepared with a constant normal free T4 concentration (12 ng/L) and varied serum T4 binding (approximately 300:1 to 24,000:1, ng protein bound T4: ng free T4). These standardized test solutions were analyzed using five T4 analog based free T4 methods. Analytical recoveries were calculated as ratios of actual free T4 measurements to the target value, and expressed as a percent of the target. Analytical recoveries were directly proportional to the extent of serum T4 binding and ranged 2% to 155%, 25% to 131%, 53% to 106%, 37% to 93%, and 37% to 73%, lowest to highest, in different methods. These systemic inaccuracies will confound interpretations of free T4 test results in clinical conditions with altered T4 binding. Future investigations into free T4 status must examine the analytical recovery of the free T4 method(s) used, as they relate to the extent of serum T4 binding in the clinical condition(s) studied.

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Evaluation of the Technicon Immuno 1 Free Thyroxine Assay

Cited by 2 publications

References 14 publications

Comparative Multicentre Study of a Panel of Thyroid Tests Using Different Automated Immunoassay Platforms and Specimens at High Risk of Antibody Interference

Comparative Multicentre Study of a Panel of Thyroid Tests Using Different Automated Immunoassay Platforms and Specimens at High Risk of Antibody Interference

Accuracy of Free Thyroxine Measurements Across Natural Ranges of Thyroxine Binding to Serum Proteins

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