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Common Mayo Medical Laboratories Test-Ordering Errors
Part 4: Overordered Tests

JAK2 on Blood and Bone Marrow
Free Thyroxine index (FTI) and T3 Uptake


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Free T4 Assays

Slide 10

July 2010

Modern direct measures of free T4, either by immunoassay or by dialysis, are much more accurate than the free thyroxine index.  The immunoassay free T4 test is the preferred, routine test. It works well and is reliable in most settings, including when thyroid binding globulin abnormalities alter total T4 levels.  The free T4 dialysis assay, is the gold standard reference method, and may be necessary in rare situations.

Free T4 Assays


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