Free Thyroxine Test System

The Free Thyroxine (FT4) Test System is a crucial diagnostic tool used to evaluate thyroid function by measuring the level of free thyroxine in the blood. FT4 is the unbound form of thyroxine, a hormone produced by the thyroid gland, which can enter body tissues to exert hormonal effects. It is essential for determining thyroid overactivity, hypothyroidism, and normal functioning.

The FT4 test works effectively with other thyroid function tests, such as TSH, to provide a clearer picture of thyroid health. Compared to the Total T4 test, which measures both bound and unbound T4, the FT4 test is more accurate as it focuses solely on the biologically active hormone.

Intended Use of Free Thyroxine Test System

A Free Thyroxine Test System is a device intended to measure free (not protein-bound) thyroxine (thyroid hormone) in serum or plasma. Levels of free thyroxine in plasma are thought to reflect the amount of thyroxine hormone available to the cells and may therefore determine the clinical metabolic status of thyroxine. Measurements obtained by this device are used in the diagnosis and treatment of thyroid diseases.

Intended Use:

Intended for the quantitative determination of Free Thyroxine levels in human serum and plasma (heparin) for the diagnosis and treatment of thyroid diseases.

Device Description:

The FT4 IV and Access Free T4 assays are advanced immunoassays designed for the in vitro quantitative determination of Free Thyroxine (FT4) in human serum and plasma, intended for use in clinical laboratory settings.

The FT4 IV, a fourth-generation assay, operates on immunoassay analyzers, utilizing Electrochemiluminescence Immunoassay (ECLIA) technology. This 18-minute competitive assay employs a monoclonal antibody specifically targeting free thyroxine. Results are determined through instrument-specific calibration using a 2-point calibration curve aligned with the reagent lot’s master curve.

The Access Free T4 assay, a two-step enzyme immunoassay, is designed for use with Access Immunoassay Systems. It consists of a reagent pack and calibrators, requiring additional components such as substrate and wash buffer. The reagent pack includes paramagnetic particles coated with streptavidin, mouse monoclonal anti-thyroxine (T4) coupled to biotin, Triiodothyronine-alkaline phosphatase conjugate, and various TRIS-buffered solutions containing proteins, surfactants, and preservatives.

• Reagent Stability
• Precision/Reproducibility
• Detection studies- Limit of Blank (LoB), Limit of Detection (LoD), and Limit of Quantitation (LoQ)
• Linearity/assay reportable range
• Traceability (controls, calibrators, or method)
• Analytical specificity
• Analytical Sensitivity
• Interfering Substances

Clinical Testing:

No Guidance available for 510k submission