Test Id : IETG
Interference Evaluation Heterophile, Thyroglobulin Tumor Marker, Serum
Useful For
Suggests clinical disorders or settings where the test may be helpful
Evaluation of suspected interference from heterophile antibodies causing a falsely elevated thyroglobulin result
Highlights
The specimen will be evaluated for potential heterophile antibody interference in the Beckman Access Thyroglobulin (Tg) Immunoassay.
In the absence of anti-thyroglobulin antibodies, the presence of heterophile interference is not suspected when the Tg concentration in the alternate platform evaluation, dilutions, and heterophile blocking tube pretreatment are substantially altered.
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 |
|---|---|---|---|
| TGII | TG, Interference Interpretation | No | Yes |
| TGQN | Thyroglobulin, Tumor Marker, S | Yes, (Order HTG2) | Yes |
| TGABI | Thyroglobulin Antibody, S | Yes, (Order HTG2) | Yes |
| TGMS | Thyroglobulin, Mass Spec., S | Yes | Yes |
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
Heterophile antibody evaluation consists of comparison of thyroglobulin (Tg) concentrations obtained by immunoassay with the following:
-Tg concentrations following pretreatment with commercial heterophile blocking reagents
-Tg concentrations obtained by mass spectrometry
-Tg concentrations obtained by serial dilutions of the sample
In all samples the presence of anti-thyroglobulin antibodies are evaluated.
Method Name
A short description of the method used to perform the test
TGII: Medical Interpretation
TGQN/TGABI: Immunoenzymatic Assay
TGMS: Tryptic Protein Fragmentation, purified with Immunocapture, Analysis by Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
(This service is performed pursuant to an agreement with SISCAPA Assay Technologies Inc. covering US Patent 7,632,686)
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
Aliases
Lists additional common names for a test, as an aid in searching
TG Heterophile
HTG
TG (Thyroglobulin)
Thyroglobulin Assay for Thyroid Cancer
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
Heterophile antibody evaluation consists of comparison of thyroglobulin (Tg) concentrations obtained by immunoassay with the following:
-Tg concentrations following pretreatment with commercial heterophile blocking reagents
-Tg concentrations obtained by mass spectrometry
-Tg concentrations obtained by serial dilutions of the sample
In all samples the presence of anti-thyroglobulin antibodies are evaluated.
Specimen Type
Describes the specimen type validated for testing
Serum Red
Ordering Guidance
If interference or heterophile testing is not required, order HTG2 / Thyroglobulin, Tumor Marker, Serum.
For fine-needle aspirate specimens, order TFNAB / Thyroglobulin, Tumor Marker, Fine-Needle Aspiration Biopsy Needle Wash.
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, patient should not take multivitamins or dietary supplements (eg, hair, skin, and nail supplements) containing biotin (vitamin B7).
Supplies: Sarstedt Aliquot Tube 5 mL (T914)
Collection Container/Tube:
Preferred: Red top
Acceptable: None (serum gel/SST are not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 2.5 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.
2 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Gross hemolysis | Reject |
| Gross lipemia | OK |
| 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 Red | Refrigerated (preferred) | 7 days | |
| Ambient | 72 hours | ||
| Frozen | 30 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
Evaluation of suspected interference from heterophile antibodies causing a falsely elevated thyroglobulin result
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
Heterophile antibody evaluation consists of comparison of thyroglobulin (Tg) concentrations obtained by immunoassay with the following:
-Tg concentrations following pretreatment with commercial heterophile blocking reagents
-Tg concentrations obtained by mass spectrometry
-Tg concentrations obtained by serial dilutions of the sample
In all samples the presence of anti-thyroglobulin antibodies are evaluated.
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, 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 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.
THYROGLOBULIN TUMOR MARKER
< or =33 ng/mL
THYROGLOBULIN, MASS SPECTROMETRY
< or =33 ng/mL
THYROGLOBULIN ANTIBODY
<1.8 IU/mL
Reference values apply to all ages.
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.
Thyroglobulin Antibody:
Thyroglobulin antibody may interfere with the measurement of Tg. TgAb should be measured in conjunction with every measurement of serum Tg to rule out potential interference. Anti-Tg antibodies greater or equal to 1.8 IU/mL are likely to cause interference in the Tg immunoassay. In the Beckman Access Tg immunoassay utilized in this interference evaluation, the presence of TgAb is most likely to cause a reduction in measured Tg concentrations. Measurement of Tg by mass spectrometry is not affected by the presence of TgAb.
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.
Thyroglobulin and anti-thyroglobulin 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;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;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;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;55(3):205-218
5. Ward G, Simpson A, Boscato L, Hickman PE. The investigation of interferences in immunoassay. Clin Biochem. 2017;50(18):1306-1311
Method Description
Describes how the test is performed and provides a method-specific reference
The specimen will be evaluated for potential heterophile antibody interference in the Beckman Coulter Access Thyroglobulin Immunoassay. Heterophile antibody evaluation will consist of measurement of thyroglobulin antibody, pretreatment with commercial heterophile antibody blocking reagents, testing on an alternate platform liquid chromatography tandem mass spectrometry, and serial dilution of the sample.
Heterophile blocking agents consist of HBT (Heterophile Blocking Tube) - Scantibodies Incorporated for the Beckman Assay. This blocker contains murine (HBT) derived proteins in a buffered salt solution.
Thyroglobulin, Tumor Marker:
The Beckman Coulter UniCel DxI 800 is the instrument used for thyroglobulin tumor marker testing. The Access Thyroglobulin (2) assay is a simultaneous one-step immunoenzymatic (sandwich) assay. the sample is added to a reaction vessel, along with a biotinylated mixture of four monoclonal anti- thyroglobulin (Tg) antibodies (TgAb), streptavidin-coated paramagnetic particles, and monoclonal anti-Tg antibody alkaline phosphatase conjugate. The biotinylated antibodies and the serum thyroglobulin bind to the solid phase, while the conjugate antibody reacts with a different antigenic site on the thyroglobulin molecule. After incubation in a reaction vessel, materials bound to the solid phase are held in a magnetic field while unbound materials are washed away. Then, the chemiluminescent substrate is added to the vessel and light generated by the reaction is measured with a luminometer. The light production is directly proportional to the concentration of thyroglobulin in the sample. The amount of analyte in the sample is determined from a stored, multi-point calibration curve(Package insert: Access Thyroglobulin. Beckman Coulter Inc.; 09/2024).
Thyroglobulin Antibody:
The Access Thyroglobulin Antibody II assay is a sequential 2-step immunoenzymatic (sandwich) assay. The sample is added to a reaction vessel with paramagnetic particles coated with Tg protein. The serum TgAb binds to the thyroglobulin. After incubation in a reaction vessel, materials bound to the solid phase are held in place by a magnetic field, while unbound materials are washed away. The Tg-alkaline phosphatase conjugate is added and binds to the TgAb. After the second incubation, materials bound to the solid phase are held in place by a magnetic field, while unbound materials are washed away. Then, the chemiluminescent substrate is added to the reaction vessel and light generated by the reaction is measured with a luminometer. The light production is directly proportional to the concentration of TgAb in the sample. The amount of analyte in the sample is calculated by means of a stored, multi-point calibration curve(Package insert: Thyroglobulin Antibody II. Beckman Coulter Inc; 09/2024).
Thyroglobulin, Alternative Method:
Serum is fractionated by a salting out method. Fractionated serum is then reduced, alkylated, and digested with trypsin. Tryptic fragments are further purified by immunocapture with antibodies specific to the individual fragments. Finally, these fragments are analyzed by liquid chromatography tandem mass spectrometry.(Unpublished Mayo method)
Thyroglobulin, Interference Interpretation:
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
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 Saturday
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.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
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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. It 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.
CPT codes are provided by the performing laboratory.
84432
86800
84432
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 |
|---|---|---|
| IETG | Interference Eval, Heterophile, TG | 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.
|
|---|---|---|
| 62749 | Thyroglobulin, Mass Spec., S | 3013-0 |
| 35998 | Interpretation | 59462-2 |
| TGABI | Thyroglobulin Antibody, S | 56536-6 |
| TGQN | Thyroglobulin, Tumor Marker, S | 96460-1 |
| TGIF | TG, Interference Heterophile | 101627-8 |
| TGIN | TG, Interpretation | 101628-6 |