part_subject: "CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES"
subpart_code: "B"
subpart_subject: "Clinical Chemistry Test Systems"
section_number: "862.1695"
section_subject: "Free thyroxine test system."
cfr_reference: "21 CFR 862.1695"
title_name: "Title 21"
title_subject: "Food and Drugs"
parts_covered: "Parts 800 to 1299"
revised_date: "Revised as of April 1, 2019"
publication_date: "As of April 1, 2019"
contains_description: "Containing a codification of documents of general applicability and future effect"
publication_info: "Published by the Office of the Federal Register National Archives and Records Administration as a Special Edition of the Federal Register"
---
(a)Identification. 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.