Test Catalog

Test Id : TGII

Not Orderable

Thyroglobulin, Interference Interpretation

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Overview

Test Catalog

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

Interpretation for the evaluation of suspected interference from heterophile antibodies causing a falsely elevated thyroglobulin result

Method Name
A short description of the method used to perform the test

Only orderable as part of profile. For more information see IETG / Interference Evaluation Heterophile, Thyroglobulin Tumor Marker, Serum.

 

Medical Interpretation

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

Yes

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

TG, Interference Interpretation

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

TG Heterophile

HTG

TG (Thyroglobulin)

Thyroglobulin Assay for Thyroid Cancer

Specimen Type
Describes the specimen type validated for testing

Serum Red

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 Red Refrigerated (preferred) 14 days
Frozen 90 days
Ambient 7 days

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

Interpretation for the evaluation of suspected interference from heterophile antibodies causing a falsely elevated thyroglobulin result

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

Serum thyroglobulin (Tg) measurements are used in the follow-up of differentiated follicular cell-derived thyroid carcinoma. Because Tg is thyroid-specific, serum Tg concentrations should be undetectable, or very low, after the thyroid gland is removed during treatment for thyroid cancer.

 

Most often Tg is measured by immunometric assays as they are widely available in automated high-throughput instruments, have shorter turnaround times, and have functional sensitivities of 0.1 mcg/L or less. However, these immunoassays may be affected by the presence of both anti-thyroglobulin antibody (TgAb) and heterophile antibody interferences. The presence of TgAb might cause falsely low/undetectable Tg that can mask disease; whereas heterophile antibodies might cause falsely high Tg that can be mistaken for residual or recurrent disease.

 

Some patients, due to exposure to animal antigens, have developed heterophile antibodies, such as human anti-mouse antibodies (HAMA), that can interfere with immunoassay testing by binding to the animal antibodies used in immunoassays. In some sandwich immunoassays, including those for Tg, the presence of heterophile antibodies in the patient’s sample might lead to a false-positive result.

Although rare, false-negative assay results due to heterophile interference have also been reported in the literature. Manufacturers often add blocking agents to their reagents, but, occasionally, patient samples containing heterophile antibodies are incompletely blocked and exhibit heterophile antibody interference. Subsequent reporting of erroneous results can have adverse effects on patient management, especially with tumor marker assays.

 

Dilution of the specimen prior to assay performance often yields unexpected nonlinear results in the presence of interfering substances such as heterophile antibodies and/or TgAb. Heterophile blocking tube (HBT) treatment is also utilized for troubleshooting samples that exhibit potential heterophile interference. Finally, assessment of an analyte such as Tg with an alternative assay will often lead to apparent discrepant results in the presence of heterophile antibodies and/or TgAb interference.

 

Measurement of Tg by liquid chromatography-tandem mass spectrometry (Tg-MS) has been introduced as a method for accurate Tg quantitation in the presence of TgAb and heterophile antibodies. Tg-MS assays are based on peptide quantitation after tryptic digestion and immunocapture of Tg-specific peptides. The advantage of trypsin digestion is that all proteins are cleaved, including both TgAb and heterophile antibodies, thus eliminating them as interferences.

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.

Only orderable as part of profile. For more information see IETG / Interference Evaluation Heterophile, Thyroglobulin Tumor Marker, Serum.

 

An interpretive report will be provided.

Interpretation
Provides information to assist in interpretation of the test results

Specimens are evaluated for the presence of potential interfering anti-thyroglobulin (TgAb) and heterophile antibody interference in the Beckman Access thyroglobulin (Tg) immunoassay. While the presence of TgAb can result in falsely low Tg concentrations in the Beckman immunoassay, the presence of heterophile antibodies can result in falsely elevated Tg concentrations in the Beckman immunoassay.  Following investigation of the presence of TgAb, heterophile antibody evaluation consists of pretreatment with commercial heterophile antibody blocking reagents, serial dilutions of the sample, and testing on an alternate platform generally unaffected by the presence of heterophile antibodies or TgAb (ie, Tg liquid chromatography-tandem mass spectrometry [Tg-MS]). The presence of heterophile antibody interference in the Beckman Access Tg immunoassay is not suspected when the results from the pretreatment, serial dilutions, and the alternative platform (Tg-MS) agree with the original result.

 

The presence of heterophile antibody interference in the Beckman Access Tg immunoassay is suspected when 1 or more of the following are observed: a significant decrease in Tg concentration (>20%) upon treatment of the sample with heterophile antibody blocking reagents, lack of linearity upon serial dilutions, or a significant difference in Tg concentration on the alternate platform (Tg-MS). When a heterophile antibody interference affecting the Beckman Access immunoassay is suspected, the Tg result from this assay is considered false-positive and should not be used in clinical management.

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

This heterophile antibody interference evaluation does not rule out the presence of other types interfering substances such as biotin.

 

There may be some samples with extremely strong heterophile interference. In such cases heterophile blocking reagents may not be able to block all the assay interference.

 

Specimens with thyroglobulin (Tg) concentrations greater than 250,000 ng/mL may "hook" and appear to have markedly lower levels.

 

Tg and anti-thyroglobulin (TgAb) values determined by different methodologies might vary significantly and cannot be directly compared with one another. Some patients might have antibody-positive results by some methods and antibody-negative results by others. Comparing values from different methods might lead to erroneous clinical interpretation.

 

Rare normal amino acid sequence variations within Tg can cause a false-low result in the Tg mass spectrometry assay, if they happen to be present in the Tg proteotypic peptides that are used for Tg quantification. While the exact prevalence of such changes is unknown, validation data on large sample numbers indicate that this affects less than 1% of samples. In the heterozygote state, the result would be an apparent reduction in Tg concentration by about 50%, while the homozygous state (<0.01%) is predicted to result in total loss of signal.

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

1. Barbesino G, Algeciras-Schimnich A, Bornhorst JA: False positives in thyroglobulin determinations due to the presence of heterophile antibodies: an underrecognized and consequential clinical problem. Endocr Pract. 2021 May;27(5):396-400. doi: 10.1016/j.eprac.2020.10.011

2. American Thyroid Association (ATA) Guidelines Taskforce on Thyroid Nodules and Differentiated Thyroid Cancer, Cooper DS, Doherty GM, et al: Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid. 2009 Nov;19(11):1167-1214

3. Netzel BC, Grebe SKG, Algeciras-Schimnich A: Usefulness of a thyroglobulin liquid chromatography-tandem mass spectrometry assay for evaluation of suspected heterophile interference. Clin Chem. 2014 Jul;60(7):1016-1018

4. Algeciras-Schimnich A: Thyroglobulin measurement in the management of patients with differentiated thyroid cancer. Crit Rev Clin Lab Sci. 2018 May;55(3):205-218

5. Ward G, Simpson A, Boscato L, Hickman PE: The investigation of interferences in immunoassay. Clin Biochem. 2017 Dec;50(18):1306-1311

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

A laboratory director will review the results and provide an interpretation.

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

No

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.

Monday through Friday

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.

3 to 5 days

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

Rochester

Fees :
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.

Not Applicable

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
TGII TG, Interference Interpretation 101626-0
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.
TGIF TG, Interference Heterophile 101627-8
TGIN TG, Interpretation 101628-6

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