Test Catalog

Test Id : T4BPE

Thyroxine-Binding Protein Electrophoresis, Serum

Useful For
Suggests clinical disorders or settings where the test may be helpful

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
A profile is a group of laboratory tests that are ordered and performed together under a single Mayo Test ID. Profile information lists the test performed, inclusive of the test fee, when a profile is ordered and includes reporting names and individual availability.

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
A short description of the method used to perform the test

TBPE: Electrophoresis

T4: Electrochemiluminescence Immunoassay

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Thyroxine-Binding Protein Electro

Lists additional common names for a test, as an aid in searching

T4 Antibodies

T4 Binders

T4 Binding Protein Electrophoresis

TBPE (Thyroxine-Binding Protein Electrophoresis)

Thyroid Binding Albumin

Thyroid Binding Prealbumin

Thyroid-Hormone Binding Electro

Thyroxine Antibodies

Thyroxine Binders

Thyroxine-Binding Protein Electrophoresis, Serum

Specimen Type
Describes the specimen type validated for testing


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
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

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

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.

0.8 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

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

Useful For
Suggests clinical disorders or settings where the test may be helpful

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

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Normally, almost all thyroxine (99.5%) is bound to thyroxine-binding globulin, prealbumin, and albumin. Deficiencies and aberrant forms of these binding proteins can occur, causing difficulties interpreting thyroid function test results. Such abnormalities may be identified by thyroxine-binding protein electrophoresis.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.


10.3-24.9 mcg T4/dL bound to thyroxine-binding globulin

11.5-34.1 mcg T4/dL bound to albumin

48.8-70.4 mcg T4/dL bound to prealbumin



Adult (> or =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

Provides information to assist in interpretation of the test results

An interpretive comment will be provided based on the total thyroxine concentration and the thyroxine binding protein profile observed on the electrophoresis.

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Thyroxine-binding globulin values may be elevated in women taking estrogens and during pregnancy.


In rare cases, some individuals can develop antibodies to mouse or other animal antibodies (often referred to as human anti-mouse antibodies [HAMA] or heterophile antibodies), which may cause interference in some immunoassays. Caution should be used in interpretation of results and the laboratory should be alerted if the result does not correlate with the clinical presentation.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Hay ID, Klee GG: Thyroid dysfunction. Endocrinol Metab Clin North Am. 1988 Sep;17(3):473-509

2. Bartalena L, Robbins J: Thyroid hormone transport proteins. Clin Lab Med. 1993 Sep;13(3):583-598

3. Mimoto MS, Refetoff S: Clinical recognition and evaluation of patients with inherited serum thyroid hormone-binding protein mutations. J Endocrinol Invest. 2020 Jan;43(1):31-41. doi: 10.1007/s40618-019-01084-9

4. Pappa T, Ferrara AM, Refetoff S: Inherited defects of thyroxine-binding proteins. Best Pract Res Clin Endocrinol Metab. 2015 Oct;29(5):735-747

Method Description
Describes how the test is performed and provides a method-specific reference

Thyroxine-binding protein electrophoresis:

Radioactive (125)I-thyroxine (T4) is incubated with patient serum, the mixture is electrophoresed on polyacrylamide gel, and the profile of binding proteins is quantitated by counting the radioactivity in slices of the gel. The binding proteins are separated by both charge and size with prealbumin on the anode side followed by albumin and thyroxine-binding globulin (TBG). Gamma globulin remains at the origin, and free T4 migrates between albumin and prealbumin. The concentration of (125)I-T4 added will saturate TBG but not the other T4-binders. The binding is expressed as thyroxine-binding capacity at 100 mcg T4/dL serum.(Unpublished Mayo method).



The Roche T4 assay is a competitive assay using electrochemiluminescence detection. Bound T4 is released from binding proteins by 8-anilino-1-naphthalene sulfonic acid (ANS). Patient specimen is incubated with sheep polyclonal anti-T4 antibody labeled with ruthenium. Streptavidin-coated microparticles and biotinylated T4 are added for a second incubation during which the still free binding sites of the labeled antibody become occupied. The resulting immunocomplex becomes bound to the solid phase by interaction of biotin and streptavidin. The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed and application of a voltage to the electrode induces the electrochemiluminescent emission. This signal is measured against a calibration curve to determine patient results.(Package insert: Elecsys T4. Roche Diagnostics; V 2.0 English 03/2020)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

One Friday per month

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

29 to 35 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

90 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their account representative. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

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
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.



LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
T4BPE Thyroxine-Binding Protein Electro 48073-1
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
T4 T4 (Thyroxine), Total Only, S 83119-8
2860 TBG 14016-0
2861 Albumin 11062-7
2862 Pre-Albumin 14014-5
2863 Abnormal Binding Protein 48767-8
3345 Comment 50681-6

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports