Test Catalog

Test Id : TTRX

Amyloidosis, Transthyretin-Associated Familial, Reflex, Blood

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

Diagnosis of adult individuals suspected of having transthyretin-associated familial amyloidosis

Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request

Mass spectrometry to evaluate transthyretin (TTR) protein structure is performed first. In all cases demonstrating a structural change, the TTR gene will be further analyzed by DNA sequence analysis. If no alterations are detected, the reflex full gene analysis will not be performed unless a specific request for ATTRZ / TTR Gene, Full Gene Analysis, Varies is submitted by the ordering physician or client.

Reflex Tests
Lists tests that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial tests.

Test Id Reporting Name Available Separately Always Performed
ATTRZ TTR Gene, Full Gene Analysis Yes No

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

If familial amyloidosis by liquid chromatography-mass spectrometry is abnormal, DNA sequence will be performed and charged separately.

 

For more information, see Amyloidosis (Familial) Test Algorithm.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

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

Affinity Chromatography/Mass Spectrometry (MS)

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

Familial Amyloidosis Reflex

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

If familial amyloidosis by liquid chromatography-mass spectrometry is abnormal, DNA sequence will be performed and charged separately.

 

For more information, see Amyloidosis (Familial) Test Algorithm.

Specimen Type
Describes the specimen type validated for testing

Whole blood

Shipping Instructions

Specimen must arrive within 96 hours of collection.

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

Container/Tube:

Preferred: Lavender top (EDTA)

Acceptable: Yellow top (ACD)

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send whole blood specimen in original tube. Do not aliquot.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Forms

If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Hematopathology/Cytogenetics Test Request (T726)

-Biochemical Genetics Test Request (T798)

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

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

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

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
Whole blood Refrigerated (preferred) 4 days
Ambient 4 days

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

Diagnosis of adult individuals suspected of having transthyretin-associated familial amyloidosis

Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request

Mass spectrometry to evaluate transthyretin (TTR) protein structure is performed first. In all cases demonstrating a structural change, the TTR gene will be further analyzed by DNA sequence analysis. If no alterations are detected, the reflex full gene analysis will not be performed unless a specific request for ATTRZ / TTR Gene, Full Gene Analysis, Varies is submitted by the ordering physician or client.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

If familial amyloidosis by liquid chromatography-mass spectrometry is abnormal, DNA sequence will be performed and charged separately.

 

For more information, see Amyloidosis (Familial) Test Algorithm.

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

The amyloidoses are a group of diseases that result from the abnormal deposition of amyloid in various tissues of the body. They have been classified into 3 major types: primary, secondary, and hereditary. The most common form of amyloidosis (AL) is a disease of the bone marrow called primary systemic AL (immunoglobulin light chain). Secondary AL usually occurs in tandem with chronic infectious or inflammatory diseases, such as rheumatoid arthritis, tuberculosis, or osteomyelitis. Familial or hereditary AL is the least common form. Determining the specific type of AL is imperative in order to provide both an accurate prognosis and appropriate therapies.

 

Familial or hereditary transthyretin AL is an autosomal dominant disorder caused by variants in the transthyretin gene (TTR). The resulting amino acid substitutions lead to a relatively unstable, amyloidogenic transthyretin (TTR) protein. Most individuals begin to exhibit clinical symptoms between the third and seventh decades of life. Affected individuals may present with a variety of symptoms including sensorimotor and autonomic neuropathy, vitreous opacities, cardiomyopathy, nephropathy, and gastrointestinal dysfunction. TTR-associated AL is progressive over a course of 5 to 15 years and usually ends in death from cardiac or kidney failure or malnutrition. Orthotopic liver transplantation is a treatment option for some patients who are diagnosed in early stages of the disease. Other treatment options include the use of TTR tetramer stabilizer medications and gene-silencing therapies (RNA interference/RNAi) recently approved for use in several countries including the United States.

 

Mayo Clinic Laboratories recommends a testing strategy that includes both protein analysis by mass spectrometry (MS) and TTR gene analysis by DNA sequencing for patients in whom TTR-associated familial AL is suspected. The structure of TTR protein in plasma is first determined by MS. The presence of a disease-causing variant in the TTR gene leads to conformational changes in the TTR protein. This ultimately disrupts the stability of the mature TTR protein tetramer, leading to increased amounts of pro-amyloidogenic TTR monomers in the plasma of affected individuals. MS technology is able to identify the mass difference between wildtype TTR and variant TTR protein. Only the transthyretin (also known as prealbumin) is analyzed for amino acid substitutions. Other proteins involved in other less common forms of familial amyloidosis are not examined. If no alterations are detected, gene analysis will not be performed unless requested by the provider (ie, when the diagnosis is still strongly suspected; to rule out the possibility of a false-negative by MS). In all cases demonstrating a structural change by MS, DNA sequence analysis will be performed on the TTR gene to identify and characterize the observed alteration (disease-causing or benign variant). More than 90 variants that cause TTR-associated familial AL have now been identified within the TTR gene. Most of the variants described to date are single base pair changes that result in an amino acid substitution. Some of these variants correlate with the clinical presentation of AL.

 

For predictive testing in cases where a familial variant is known, testing for the specific variant by DNA sequence analysis (FMTT / Familial Mutation, Targeted Testing, Varies) is recommended. These assays do not detect alterations associated with non-TTR forms of familial AL. Therefore, it is important to first test an affected family member to determine if TTR is involved and to document a specific alteration in the family before testing at-risk individuals.

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.

An interpretive report will be provided.

Interpretation
Provides information to assist in interpretation of the test results

The presence of a structural change in transthyretin (TTR) is suggestive of a gene variant that requires confirmation by DNA sequence analysis. A negative result by mass spectrometry does not rule out a TTR variant. Mass spectrometric (MS) results are falsely negative if the amino acid substitution does not produce a measurable mass shift for the transthyretin variant. Approximately 90% of the TTR variants are positive by MS (see Cautions).

 

After identification of the variant at the DNA level, predictive testing for at-risk family members can be performed by molecular analysis (FMTT / Familial Mutation, Targeted Testing, Varies).

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

There are 3 circumstances where testing by mass spectrometry will not identify amyloid-causing variants:

-If the amino acid change results in a protein different by less than 10 atomic mass units (amu), the genetic variant will not be reliably detected.

-If an amino acid change results from a frequent nondisease-causing alteration (+30 amu). Since over 12% of the population has this innocuous alteration, it is an instance in which molecular testing must be done.

-Coinheritance of the alteration with a -30 amu variant would result in a transthyretin mass indistinguishable from normal.

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

1. Sekijima Y: Hereditary transthyretin amyloidosis. In: Adam MP, Ardinger HH, Pagon RA, et al, eds. GeneReviews [Internet]. University of Washington, Seattle; 2001. Updated June 17, 2021 Accessed January 5, 2022. Available at www.ncbi.nlm.nih.gov/books/NBK1194/

2. Finsterer J, Iglseder S, Wanschitz J, et al: Hereditary transthyretin-related amyloidosis. Acta Neurol Scand. 2019 Feb;139(2):92-105

3. Sekijima Y. Transthyretin (ATTR) amyloidosis: clinical spectrum, molecular pathogenesis and disease-modifying treatments. J Neurol Neurosurg Psychiatry. 2015 Sep;86(9):1036-1043. doi: 10.1136/jnnp-2014-308724

Special Instructions
Library of PDFs including pertinent information and forms related to the test

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

Familial Amyloidosis, Mass Spectrometry (MS):

Transthyretin (TTR) is purified from plasma using online affinity chromatography coupled to a quadrupole time-of-flight mass spectrometer. The acquired ion spectra are deconvoluted and reviewed for TTR variants. After deconvolution, normal patients present with a single peak corresponding to wildtype (wt) TTR, which serves as a reference. When positive, amyloid patients are typically heterozygous and are detected by the presence of 2 peaks (ie, wt TTR and altered TTR) differing in mass.(Bergen HR 3rd, Zeldenrust SR, Butz ML, et al: Identification of transthyretin variants by sequential proteomic and genomic analysis. Clin Chem. 2004 Sep;50[9]:1544-1552; Trenchevska O, Yassine HN, Borges CR, et al. Development of quantitative mass spectrometric immunoassay for serum amyloid A. Biomarkers. 2016 Dec;21(8):743-751)

 

TTR Gene, Full Gene Analysis:

All 4 exons of the TTR gene are amplified by PCR and then subjected to direct DNA sequence analysis.(Bergen RH 3rd, Zeldenrust SR, Butz ML, et al: Identification of transthyretin variants by sequential proteomic and genomic analysis. Clin Chem. 2004 Sept;50(9):1544-1552)

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.

Tuesday

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 9 days

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

2 months

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 Regional Manager. 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.

82542

81404 (if appropriate)

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
TTRX Familial Amyloidosis Reflex 94864-6
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.
22668 Wild Type Mass 94860-4
22669 Wild Type Width at Half Height 94863-8
22670 Second Mass 94862-0
22671 Mass Difference 94861-2
22673 Abnormal result 51968-6
50944 Interpretation 69047-9
50946 Reviewed By 18771-6

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