Test ID: FRTEL
Subtelomeric Region Anomalies, FISH
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
Evaluation of cases of nonspecific moderate-to-severe mental retardation or nonspecific dysmorphic features when standard chromosome results are normal
Evaluation of parents or other family members of a patient who has been previously diagnosed with a subtelomere abnormality
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
Fluorescence In Situ Hybridization (FISH) with DNA Probes
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
FISH for Cryptic Telomere Abnormalities
FISH for Telomeres
FISH of Subtelomeric regions
Subtelomere
Subtelomeric FISH
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.
Provide a reason for referral with each specimen. The laboratory will not reject testing if this information is not provided, but appropriate testing and interpretation may be compromised or delayed.
Forms:
1. 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.
2. If not ordering electronically, submit a Cytogenetics/AFP Congenital Disorders Request Form (Supply T238) with the specimen.
Advise Express Mail or equivalent if not on courier service.
Submit only 1 of the following specimens:
Preferred:
Specimen Type: Blood
Container/Tube: Green top (sodium heparin)
Specimen Volume: 5 mL
Collection Instructions:
1. Invert several times to mix blood.
2. Other anticoagulants are not recommended and are harmful to the viability of the cells.
Acceptable:
Specimen Type: Amniotic fluid
Container/Tube: Amniotic fluid container
Specimen Volume: 20-25 mL
Collection Instructions:
1. Optimal timing for specimen collection is during 14 to 18 weeks of gestation, but specimens collected at other weeks of gestation are also accepted. Provide gestational age at the time of amniocentesis.
2. Discard the first 2 mL of amniotic fluid.
Additional Information:
1. Place the tubes in a Styrofoam container (Supply T329).
2. Fill remaining space with packing material.
3. Unavoidably, about 1% to 2% of mailed-in specimens are not viable.
4. Bloody specimens are undesirable.
5. If the specimen does not grow in culture, you will be notified within 7 days of receipt.
6. Results will be reported and also telephoned or faxed, if requested.
Specimen Type: Chorionic villi
Container/Tube: 15-mL tube containing 15 mL of transport medium
Specimen Volume: 20-25 mg
Collection Instructions:
1. Collect specimen by the transabdominal or transcervical method.
2. Transfer chorionic villi to a Petri dish containing transport medium (Supply T095).
3. Using a stereomicroscope and sterile forceps, assess the quality and quantity of the villi and remove any blood clots and maternal decidua.
Specimen Type: Products of conception or stillbirth
Container/Tube: Sterile container with sterile Hank's balanced salt solution (Supply T132), Ringer's solution, or normal saline
Specimen Volume: 1 cm(3) of placenta (including 50-mg of chorionic villi) and a 1-cm(3) biopsy specimen of muscle/fascia from the thigh
Collection Instruction: If a fetus cannot be specifically identified, collect villus material or tissue that appears to be of fetal origin.
Additional Information: Do not send entire fetus.
Forms: Final Disposition of Fetal/Stillborn Remains (if fetal specimen is sent) in Special Instructions
Specimen Type: Skin biopsy
Container/Tube: Sterile container with sterile Hank's balanced salt solution (Supply T132), Ringer's solution, or normal saline
Specimen Volume: 4 mm diameter
Collection Instructions:
1. Wash biopsy site with an antiseptic soap.
2. Thoroughly rinse area with sterile water.
3. Do not use alcohol or iodine preparations.
4. A local anesthetic may be used.
5. Biopsy specimens are best taken by punch biopsy to include full thickness of dermis.
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 | Clotted blood |
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 |
|---|---|---|
| Varies | Ambient (preferred) | |
| Refrigerated | ||
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Telomere caps of (TTAGGG)n repeats constitute 3 Kb to 20 Kb at the ends of each human chromosome. Centromeric to the telomere caps are 100 Kb to 300 Kb of telomere-associated repeats (TAR). Unique DNA sequences are centromeric to the TAR ending. The telomere-specific DNA probes are derived from the area near the junction of the TARs and unique sequences.(1)
Because of high gene concentrations in telomeric regions(2), there is an intense interest in subtle abnormalities involving the telomeres. For example, subtle abnormalities have been reported involving the telomeres in 7.4% of a large population of children with moderate-to-severe mental retardation.(3) Abnormalities involving the telomere regions also are suspected in individuals with nonspecific dysmorphic features or couples with multiple miscarriages who are karyotypically normal.
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
A deletion results in the loss of a p-arm or q-arm specific probe, and a cryptic translocation causes an exchange between the involved chromosome arms. Duplications, derivative chromosomes, and insertions of subtelomeric regions also can be detected.
Family studies may be necessary following abnormal results from this FISH study, as parents may carry balanced translocations or deletions that are found in their children.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
A standard chromosome analysis must be performed first to rule out microscopically observable karyotypic abnormalities.
Microdeletions that are outside of the probe location are undetectable and this test cannot detect DNA molecular alterations such as point mutations.
If original specimen is of low volume or has low number of suitable metaphases, another specimen may be necessary for this test, since this test requires large quantities of metaphases.
Supportive Data
We have validated the hybridization efficiency of the telomere-specific FISH probe set in a variety of cases.
A total of 22 couples with multiple miscarriages were analyzed, who were karyotypically normal and had no apparent abnormality of the telomere regions. However, 5 of these individuals had a deletion of the 2q telomere-specific probe (D2S2986). Additionally, the deletion was observed in a child with multiple dysmorphic features, as well as his clinically normal parent. As a result, deletions involving this probe are presumed to be normal population variants. This has proven to be a normal deletion variant because it was not deleted when the 2q subtelomere-specific probe of another commercial company was used. For several chromosome telomeres (2p, 3q, 4p and q, 8p and q, 9q, 11p and q, 12p, 15q, 16q, 17p and q, 18p, 20q and 22q), some cross-hybridizations to other chromosomal regions occurred, but they were distinct, often weak, and easily discernible. Other potential "normal variants" have been reported in the literature, so parental testing and clinical correlation is recommended whenever a subtelomere abnormality is identified.
Our experience based on the analysis of 2237 patients indicates that subtelomeric abnormalities occur in approximately 7.4% of individuals tested. The anomalies found included deletions, duplications, derivative chromosomes, and reciprocal translocations. However, no more than 50% of these were subtle or cryptic. This test is also helpful in describing subtelomere anomalies in a timely manner that are ambiguous by banded chromosome analysis.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Knight SJ, Lese CM, Precht S, et al: An optimized set of human telomere clones for studying telomere integrity and architecture. Am J Hum Genet 2000;67:320-332
2. Saccone S, DeSario A, Della Valle G, et al: The highest gene concentrations in the human genome are in telomeric bands of metaphase chromosomes. Proc Natl Acad Sci USA 1992;89:4913-4917
3. Knight SJ, Regan R, Nicod A, et al: Subtle chromosomal rearrangements in children with unexplained mental retardation. Lancet 1999;354:1676-1681
Method Description Describes how the test is performed and provides a method-specific reference
The subtelomere-specific FISH test is done with commercially available DNA fluorescent probes for each chromosome. Each chromosome is separately analyzed. At least 3 metaphases are analyzed with each p-arm and q-arm probe pair. A total of 41 telomere-specific probes are used. These probes hybridize specifically to the respective TAR region of each chromosome, with the exception of the 5 p-arms of acrocentric chromosomes, which do not have unique sequences. The processing time is usually 24 hours, and the test can be performed on cultured lymphocytes or fibroblasts. (Jalal SM, Harwood AR, Sekhon GS, et al: Utility of subtelomeric fluorescent DNA probes for detection of chromosome anomalies in 425 patients. Genet Med 2003;5:28-34)
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.
Samples processed Monday through Sunday. Results reported Monday through Friday, 8 a.m.-5 p.m. CST.
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.
88271 x 41-DNA probe, each
88273 x 2-Chromosomal in situ hybridization
88291-Interpretation and report
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 |
|---|---|---|
| 17184 | Specimen | 31208-2 |
| 17185 | Specimen ID | N/A |
| G_547 | Source | N/A |
| 17187 | Order Date | N/A |
| G_549 | Reason For Referral | 42349-1 |
| 17188 | Method | In Process |
| 17190 | Results | In Process |
| 17191 | Interpretation | 69965-2 |
| 17192 | Amendment | In Process |
| 17193 | Consultant | N/A |
| 17194 | Report Date | N/A |
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