Home


T4F
T4 (THYROXINE), FREE, SERUM

Test Code T4F 
Test T4 (THYROXINE), FREE, SERUM 
Methodology Electrochemiluminescence Immunoassay (ECLIA) 
Description Useful for obtaining a more accurate assessment of thyroid status in patients with abnormal T4-binding protein levels, including those who are pregnant or receiving steroid therapy.

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.

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. Free T4 may be artificially elevated by heparin. Spin down and send 1.0 mL (minimum volume: 0.5 mL) of serum refrigerated. 
Reference Values 0.9 - 1.7 ng/dL 
Analytic Time 1 Day 
Day(s) Test Set Up Monday through Sunday 
CPT Code(s) 84439