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Test 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.

 

This test is not appropriate for measuring telomere length or testing for telomere shortening.

Method Name

Fluorescence In Situ Hybridization (FISH)

Reporting Name

Subtelomeric Region Anomalies, FISH

Specimen Type

Varies


Shipping Instructions


Advise Express Mail or equivalent if not on courier service.



Necessary Information


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.



Specimen Required


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:

Supplies: Refrigerate/Ambient Mailer, 5 lb (T329)

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.

3. Place the tubes in a 5-lb Refrigerate/Ambient Mailer (T329).

4. Fill remaining space with packing material.

Additional Information:

1. Unavoidably, about 1% to 2% of mailed-in specimens are not viable.

2. Bloody specimens are undesirable.

3. If the specimen does not grow in culture, you will be notified within 7 days of receipt.

4. Results will be reported and also telephoned or faxed, if requested.

 

Supplies: CVS Media (RPMI) and Small Dish (T095)

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 (such as CVS Media (RPMI) and Small Dish [T095]).

3. Using a stereomicroscope and sterile forceps, assess the quality and quantity of the villi and remove any blood clots and maternal decidua.

 

Supplies: Hank's Solution (T132)

Specimen Type: Products of conception or stillbirth

Container/Tube: Sterile container with sterile Hank's balanced salt solution (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.

 

Supplies: Hank's Solution (T132)

Specimen Type: Skin biopsy

Container/Tube: Sterile container with sterile Hank's balanced salt solution (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) of 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.

Interpretation

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.

Clinical Reference

1. Knight SJ, Regan R, Nicod A, et al: Subtle chromosomal rearrangements in children with unexplained mental retardation. Lancet 1999;354:1676-1681

2. 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) Performed

Samples processed Monday through Sunday. Results reported Monday through Friday, 8 a.m. to 5 p.m. CST.

Analytic Time

11 days

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

88271 x 2, 88291-DNA probe, each (first probe set), Interpretation and report

88271 x 2 DNA probe, each; each additional probe set (if appropriate)

88271 x 1-DNA probe, each; coverage for sets containing 3 probes (if appropriate)

88271 x 2-DNA probe, each; coverage for sets containing 4 probes (if appropriate)

88271 x 3-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)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
TELOF Subtelomeric Region Anomalies, FISH In Process

 

Result ID Test Result Name Result LOINC Value
51985 Result Summary 50397-9
51987 Interpretation In Process
54562 Result In Process
CG711 Reason for Referral 42349-1
CG712 Specimen 31208-2
51988 Source 31208-2
51989 Method 49549-9
51986 Additional Information 48767-8
53853 Disclaimer 62364-5
51990 Released By No LOINC Needed

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 (T576) is available in Special Instructions.

2. Final Disposition of Fetal/Stillborn Remains (if fetal specimen is sent) in Special Instructions

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

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