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Test ID T4BPE Thyroxine-Binding Protein Electrophoresis, Serum

Useful For

Explaining unusual thyroxine (T4), free T4, and thyroxine-binding globulin (TBG) test results that do not correlate with the patient’s clinical presentation


Detecting the presence of aberrant thyroxine-binding proteins such as abnormal forms of albumin and prealbumin


Detecting selective deficiency of one of the thyroxine-binding proteins


Detecting antibodies to T4


An adjunct to the diagnosis of patients with high T4 concentration due to peripheral hormone resistance by ruling out thyroxine-binding abnormalities

Profile Information

Test ID Reporting Name Available Separately Always Performed
TBPE Thyroxine-Binding Protein Electro No Yes
T4 T4 (Thyroxine), Total Only, S Yes Yes

Method Name

TBPE: Electrophoresis

T4: Electrochemiluminescence Immunoassay

Reporting Name

Thyroxine-Binding Protein Electro

Specimen Type


Ordering Guidance

This assay measures thyroxine binding to various proteins.


For analysis of thyroxine-binding globulin, see TBGI / Thyroxine-Binding Globulin (TBG), Serum.

For immunologic assay of prealbumin, see PALB / Prealbumin, Serum.


This test should not be requested in patients who have recently received radioisotopes, therapeutically or diagnostically, because of potential assay interference. A recommended time period before collection cannot be made because it will depend on the isotope administered, the dose given, and the clearance rate in the individual patient.


The total T4 test should not be used in patients receiving treatment with lipid-lowering agents containing dextrothyroxine unless therapy is discontinued for 4 to 6 weeks to allow the T4 physiological state to become re-established prior to testing.

Specimen Required

Patient Preparation: For 12 hours before specimen collection, do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1.6 mL

Specimen Minimum Volume

0.8 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days
  Frozen  30 days
  Ambient  24 hours

Reference Values


10.3-24.9 mcg T4/dL bound to TBG

11.5-34.1 mcg T4/dL bound to albumin

48.8-70.4 mcg T4/dL bound to prealbumin



Adult (≥20 years): 4.5-11.7 mcg/dL


0-5 days: 5.0-18.5 mcg/dL

6 days-2 months: 5.4-17.0 mcg/dL

3-11 months: 5.7-16.0 mcg/dL

1-5 years: 6.0-14.7 mcg/dL

6-10 years: 6.0-13.8 mcg/dL

11-19 years: 5.9-13.2 mcg/dL

Day(s) Performed

One Friday per month

Report Available

2 to 29 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 US Food and Drug Administration.

CPT Code Information



LOINC Code Information

Test ID Test Order Name Order LOINC Value
T4BPE Thyroxine-Binding Protein Electro 48073-1


Result ID Test Result Name Result LOINC Value
2860 TBG 14016-0
2861 Albumin 11062-7
T4 T4 (Thyroxine), Total Only, S 83119-8
2862 Pre-Albumin 14014-5
2863 Abnormal Binding Protein 48767-8
3345 Comment 50681-6

NY State Approved