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TUP
T4 (THYROXINE), UPTAKE, SERUM

Test Code TUP 
Test T4 (THYROXINE), UPTAKE, SERUM 
Methodology Electrochemiluminescence Immunoassay (ECLIA) 
Description Useful for assessment of unsaturated thyroid hormone binding sites in serum; evaluating patients to determine whether changes in T3 and T4 levels are due to changes in hormone production or levels of binding proteins.

NOTE: This test, when ordered on Medicare patients, is subject to the National Coverage Determination (NCD) policy "Thyroid Testing". Please verify that the diagnosis code (ICD-9) you have chosen demonstrates medical necessity for the test as documented in the physician's patient record. The CMS web site or the NorDx Limited Coverage Documentation Guide are available to assist you with this verification. A properly executed Advance Beneficiary Notice (ABN) must be submitted with the specimen if medical necessity is not demonstrated by the ICD-9 code chosen.

No sample should be collected on patients receiving therapy with high biotin doses (i.e. biotin therapy for Multiple Sclerosis or oncology patients; skin, hair and nail supplements, or multivitamins containing > 5 mg/day) until at least 12 hours after the last biotin administration. If unsure, or if the clinical picture does not fit the results please contact the laboratory . We have methods to check for biotin interference as well as for any other interferences and for the accuracy of the results.

Biotin interference would falsely increase the result of this assay. 

Specimen Draw blood in either a plain, red-top tube or serum gel tube. Spin down and send 1.0 mL (minimum volume: 0.5 mL) of serum refrigerated. 
Reference Values 0.8 - 1.3 TBI 
Analytic Time 1 Day 
Day(s) Test Set Up Monday through Friday 
CPT Code(s) 84479