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Test Code FRT4D T4 (Thyroxine), Free by Dialysis, Serum


Advisory Information


The routine free thyroxine (FT4) test (FRT4 / T4 [Thyroxine], Free, Serum) is faster and provides useful information in most patients.



Necessary Information


Include name and telephone number of contact physician.



Specimen Required


Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 2.6 mL

Collection Instructions:

1. Draw blood immediately before next scheduled dose.

2. Centrifuge and separate serum from cells or gel within 2 hours of draw.


Useful For

Determining thyroid status of sick, hospitalized patients

 

Determining thyroid status of patients in whom abnormal binding proteins have been identified

 

Possibly useful in pediatric patients

Method Name

Equilibrium Dialysis/Tandem Mass Spectrometry (MS/MS)

Reporting Name

T4 (Thyroxine), Free by Dialysis, S

Specimen Type

Serum

Specimen Minimum Volume

1.2 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 28 days
  Frozen  21 days
  Ambient  7 days

Reject Due To

Hemolysis

Mild OK; Gross reject

Lipemia

Mild reject; Gross reject

Icterus

Mild OK; Gross reject

Other

NA

Reference Values

0.8-2.0 ng/dL

Reference values apply to all ages.

Day(s) and Time(s) Performed

Monday, Wednesday, Thursday; 3 p.m.

Analytic Time

3 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

84439 

LOINC Code Information

Test ID Test Order Name Order LOINC Value
FRT4D T4 (Thyroxine), Free by Dialysis, S 6892-4

 

Result ID Test Result Name Result LOINC Value
8859 T4 (Thyroxine), Free by Dialysis, S 6892-4