Laboratory analysis of the thyroid hormones and thyroid function tests span the range of analytical principles. Most clinical laboratories with an automated immunoassay system offer a menu of free T4, free T3 and thyroid-stimulating hormone (TSH), with a smaller number offering thyroid autoantibody testing.
|Spectrophotometric||Historical methods for the analysis of total T4 and T3 employed sprectrophotometric principles, some of which were automated on general chemistry analyzers for high-throughput screening.|
|Radioimmunoassay (RIA)||Many of the first automated thyroid hormone assays and TSH methods employed RIA. Now, less frequently used, with the exception of reverse T3 assays.|
|Enzyme-linked immunosorbent assay (ELISA)||ELISA principles dominate the manual microplate assays, which are used less frequently in laboratories with an automated immunoassay system.|
|Fluorescence polarization immunoassay (FPIA)||Once a fairly commonly used principle in laboratories transitioning from RIA methods, less commonly used today.|
|Chemiluminescence immunoassay (CIA)||One of the most commonly used principles in automated immunoassay systems, providing enhanced sensitivity and precision.|
|High-performance liquid chromatography (HPLC) and LC-mass-spectrometry (LC-MS)||Chromatographic methods typically have the highest achievable degree of sensitivity and are free from non-specific interferences with heterophile antibodies. Not widely used in small-to-mid-size laboratories.|
On the pages to follow, a more detailed overview is provided on the laboratory analysis of the thyroid markers.