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HelpTest ID TELOF Subtelomeric Region Anomalies, FISH
Useful For
Diagnosis of subtelomeric chromosome abnormalities and rearrangements
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| _M30 | Metaphases, ≥10 | No, (Bill Only) | No |
| _ML10 | Metaphases, 1-9 | No, (Bill Only) | No |
| _PADD | Probe, +1 | No, (Bill Only) | No |
| _PB02 | Probe, +2 | No, (Bill Only) | No |
| _PB03 | Probe, +3 | No, (Bill Only) | No |
| _PBCT | Probe, +2 | No, (Bill Only) | No |
Testing Algorithm
This test includes a charge for application of the first probe set (2 FISH probes) and professional interpretation of results. Additional charges will be incurred for all reflex probes performed. Analysis charges will be incurred based on the number of cells analyzed per probe set. If no cells are available for analysis, no analysis charges will be incurred.
Special Instructions
Method Name
Fluorescence In Situ Hybridization (FISH)
Reporting Name
Subtelomeric Region Anomalies, FISHSpecimen Type
VariesProvide 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: 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.
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
Amniotic Fluid: 5 mL/Blood: 2 mL/Chorionic Villi: 5 mg/Products of Conception: 1 cm(3)/Skin Biopsy: 4 mm
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Varies | Refrigerated (preferred) | |
| Ambient | ||
Clinical Information
This test is appropriate for individuals with clinical features including intellectual disability, developmental delay, mental retardation, autism, dysmorphic features, behavior disorders, learning disability, cognitive impairment of unknown etiology or individuals with a family member previously diagnosed with a subtelomere abnormality.
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 investigated for this test 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.
Because of high gene concentrations in telomeric regions, 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.
Abnormalities involving the telomere regions also are suspected in individuals with nonspecific dysmorphic features or couples with multiple miscarriages who are karyotypically normal.
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.
Reference Values
An interpretive report will be provided.
Cautions
Because this FISH test is not approved by the U.S. Food and Drug Administration, it is important to confirm subtelomeric rearrangements by other established methods, including clinical history and physical evaluation.
Chromosomal microarray (CMAC / Chromosomal Microarray, Congenital, Blood or CMAP / Chromosomal Microarray, Prenatal) may be the more appropriate test to detect unbalanced translocations, deletions or duplications.
Interfering factors
- Cell lysis caused by forcing the blood quickly through the needle
- Use of an improper anticoagulant or improperly mixing the blood with the anticoagulant
- Excessive transport time
- Inadequate amount of specimen may not permit adequate analysis
- Improper packaging may result in broken, leaky, and contaminated specimen during transport
- Exposure of the specimen to temperature extremes (freezing or >30° C) may kill cells and interfere with attempts to culture cells
- In prenatal specimens, a bloody specimen may interfere with attempts to culture cells and contamination by maternal cells may cause interpretive problems
Day(s) Performed
Samples processed Monday through Sunday. Results reported Monday through Friday, 8 a.m. to 5 p.m. CST.
Report Available
11 daysPerforming Laboratory
Mayo Medical Laboratories in Rochester
Test Classification
This test was developed using an analyte specific reagent. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.CPT Code Information
88271x2, 88291 – DNA probe, each (first probe set), Interpretation and report
88271x2 – DNA probe, each; each additional probe set (if appropriate)
88271x1 – DNA probe, each; coverage for sets containing 3 probes (if appropriate)
88271x2 – DNA probe, each; coverage for sets containing 4 probes (if appropriate)
88271x3 – DNA probe, each; coverage for sets containing 5 probes (if appropriate)
88273 w/modifier 52-Chromosomal in situ hybridization, less than 10 cells (if appropriate)
88273-Chromosomal in situ hybridization, 10-30 cells (if appropriate)