Test ID: TACIG
Transmembrane Activator and CAML Interactor (TACI) Gene, Known Mutation Analysis
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Identifying the presence of a TACI mutation in a symptomatic patient when the mutation has been identified in an affected family member
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 |
|---|---|---|---|
| TACIM | TACI Gene, Known Mutation | No | Yes |
| TACIK | TACI Known Mutation Sequencing | No | Yes |
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
Polymerase Chain Reaction (PCR) Followed by DNA Sequence Analysis
(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
APRIL receptor
Autoimmune cytopenias
B-cells
BAFF receptor
Common variable immunodeficiency
CVID
Hypogammaglobulinemia
IgA deficiency
Isotype class switching
Malignancy in CVID
sIgAD
T-cell-independent antibody response
TACI
TNFRSF13B
Transmembrane Activator and CAML interactor
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
This test is only applicable if a mutation has previously been identified in a family member of this individual.
Multiple whole blood EDTA genotype tests can be performed on a single specimen after a single extraction. See Multiple Whole Blood EDTA Genotype Tests in Special Instructions for a list of tests that can be ordered together.
Container/Tube: Lavender top (EDTA)
Specimen Volume: 3 mL
Collection Instructions: Send specimen in original tube.
Additional Information:
1. Ordering physician's name and phone number are required.
2. Bone marrow transplants will interfere with testing. Call Mayo Medical Laboratories at 800-533-1710 or 507-266-5700 for instructions.
3. Transfusions will interfere with testing for up to 4 to 6 weeks. DNA obtained from white cells may not provide useful information for patients who received a recent transfusion of blood that was not leukocyte-reduced. Wait 4 to 6 weeks until transfused cells have left the patient's circulation before drawing the patient's blood specimen for genotype testing.
Forms:
1. TACI Genotyping Patient Information Sheet (Supply T604) in Special Instructions.
2. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Whole Blood EDTA | Ambient (preferred) | |
| Refrigerated | ||
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Transmembrane activator and CAML interactor (TACI) is a member of the tumor-necrosis factor (TNF)-like receptor family, a group of receptors that regulate both survival and apoptosis of immune cells.(1) TACI is expressed on the surface of resting B cells and activated T cells, but not resting T cells. TACI interacts with 2 ligands-BAFF (B-cell activating factor), also known as BLys (B-lymphocyte stimulator), which belongs to the TNF family, and APRIL (a proliferation-inducing ligand). The ligands for TACI are expressed on macrophages, monocytes, and dendritic cells.(1) TACI regulates isotype class-switching of immunoglobulins and also is involved in the antibody response to T-independent antigens.(2)
TACI is encoded by the TACI gene (official symbol, TNFRSF13B). The human TACI gene locus is located on the short arm of chromosome 17, which is a common target for mutation and rearrangement.(2) The TACI gene consists of 5 exons spanning approximately 35 kb (including 1002 bp upstream of the 5' untranslated region [UTR] and 1024 bp downstream of the 3' UTR). The mRNA length is 1377 bp, encoding for a 294-amino acid protein with a molecular weight of 32.34 kD. Six mutations (D68X [also called L69fsX11], C104R, S144X, A181E, S194X, and R202H) were identified in the TACI gene in the original reports.(3,4) Of these 6 mutations, 4 (D68X, C104R, A181E, and R202H) have been shown to be statistically significant in common variable immunodeficiency (CVID) and selective IgA deficiency (sIgAD) patients, when compared to controls.(5) Several other mutations have been reported, but none of these appear to be statistically significant when compared to controls.(5) Two other mutations, P251L and V220A, are considered to be rare polymorphisms as they are present in both controls and patients.(3-5) The TACI mutations described so far are nonsense, missense, or frameshift (due to the insertion of a single extra nucleotide) mutations, all of which can be detected by gene sequencing. No large deletions or duplications have been reported for this gene at this time.
TACI mutations account for 8% to 15% of CVID cases depending on the study population and are sporadic in the majority of cases. The familial TACI mutations can be inherited in either an autosomal dominant or autosomal recessive fashion. There also appears to be variable penetrance in the familial TACI mutations.(7) TACI mutations appear to be strongly associated with lymphoproliferative diseases such as splenomegaly or tonsillar hypertrophy. Autoimmune thyroiditis is observed in 15% of TACI mutation-positive CVID cases. The incomplete penetrance seen for TACI mutations indicates that a mutation can be present, but the individual does not develop the disease phenotype.
The known TACI mutations appear, in most cases, to be associated with normal protein expression with aberrant or absent functional activity and require gene sequencing analysis to confirm the presence of the mutation as well as correlation with the clinical phenotype.
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
An interpretive report will be provided that describes the presence or absence of the previously identified mutation(s), and their potential clinical significance. Variants of unknown clinical significance within the specific exon being evaluated also will be documented in the report.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This test will only determine if the specific mutation previously described in a family member is present or not.
Only symptomatic family members of an affected patient, in whom a mutation has been identified, should be tested with this assay.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Mackay F, Ambrose C: The TNF family members BAFF and APRIL: the growing complexity. Cytokine Growth Factor Rev 2003;14:311-324
2. Castigli E, Geha RS: Molecular basis of common variable immunodeficiency. J Allergy Clin Immunol 2006;117:740-746
3. Castigli E, Wilson SA, Garibyan L, et al: TACI is mutant in common variable immunodeficiency and IgA deficiency. Nat Genet 2005;37(8):829-834
4. Salzar U, Chapel HM, Webster ADB, et al: Mutations in TNFRSF13B encoding TACI are associated with common variable immunodeficiency in humans. Nat Genet 2005;37(8):820-828
5. Castigli E, Wilson S, Garibyan L, et al: Reexamining the role of TACI coding variants in common variable immunodeficiency and selective IgA deficiency. Nat Genet 2007;39(4):429-431
Method Description Describes how the test is performed and provides a method-specific reference
Genomic DNA is extracted from whole blood, followed by TACI gene amplification by PCR for the specific exon. The PCR product is separated from unincorporated primers, nucleotides, and contaminants by column purification, then sequenced in both directions using sequencing primers and fluorescent dye-terminator chemistry. The sequencing product is separated on an automated sequencer and trace files analyzed for variations in the specific exon and intron/exon boundaries using specialized mutation detection software and visual inspection (unpublished Mayo method).
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Wednesday
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
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 The location of the laboratory that performs the test
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's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
81479 -Unlisted molecular pathology procedure
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 28588 | Reason for Referral | 42349-1 |
| TACIQ | Sequencing | N/A |
| 28589 | Method | In Process |
| 28590 | Result | In Process |
| 28591 | Interpretation | 69047-9 |
| 28593 | Reviewed By | N/A |
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