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Test ID: BP1F 15q Deletion, Type I and Type II Characterization, Prader-Willi/Angelman Syndromes, FISH

Useful For

Differentiating between type I and type II deletions in patients with a known deletion of 15q11.1-11.3, causative of Prader-Willi syndrome or Angelman

 

Evaluation of dic(15) marker chromosomes

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
_PBCT Probe, +2 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
_ML10 Metaphases, 1-9 No, (Bill Only) No
_M30 Metaphases, ≥10 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 application of 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.

Method Name

Fluorescence In Situ Hybridization (FISH)

Reporting Name

15q Del Characterization, FISH

Specimen Type

Varies


Advisory Information


This test can only be performed if a known SNRPN or D15S10 deletion has been previously identified by FISH analysis or in patients with a dic(15) chromosome.

 

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.



Shipping Instructions


Advise Express Mail or equivalent if not on courier service.



Specimen Required


Submit only 1 of the following specimens:

 

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 Refrigerate/Ambient Mailer. 5 lb (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: Hank's Solution (T132)

Specimen Type: Autopsy

Container/Tube: Sterile container with sterile Hank's solution (T132), Ringer's solution, or normal saline

Specimen Volume: 1 cm(3) biopsy specimen of muscle/fascia from the thigh

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. Biopsy specimens are best taken by punch biopsy to include full thickness of dermis.

 

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.

 

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

Specimen Type: Chorionic villi

Container/Tube: 15-mL tube containing 15 mL of transport media

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.

 

Specimen Type: Fixed cell pellet

Container/Tube: Sterile container with a 3:1 fixative (methanol:glacial acetic acid)

Specimen Volume: Entire specimen

 

Supplies: Hank's Solution (T132)

Specimen Type: Products of conception or stillbirth

Container/Tube: Sterile container with sterile Hank's solution (T132), Ringer's solution, sterile RPMI transport media, or normal saline

Specimen Volume: 1 cm(3) of placenta (including 20 mg of chorionic villi) and a 1-cm(3) biopsy specimen of muscle/fascia from the thigh

Collection Instructions: 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 solution (T132), Ringer's solution, or normal saline

Specimen Volume: 1-cm(3) biopsy specimen of muscle/fascia from the thigh

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; Autopsy, Skin Biopsy: 4 mm; Blood: 2 mL; Chorionic Villi: 5 mL; Fixed Cell Pellet: 1 pellet; Products of Conception: 1 cm(3)

Specimen Stability Information

Specimen Type Temperature Time
Varies Refrigerated (preferred)
  Ambient 

Clinical Information

Prader-Willi (PWS) and Angelman (AS) syndromes are 2 distinct syndromes that can result from either a paternal or maternal deletion of 15q11-q13, respectively. Other mechanisms of inheritance include maternal uniparental disomy (UPD) in PWS, paternal UPD in AS, or abnormal methylation and gene expression.

 

Both type I and type II 15q11-q13 deletions have been described. Type 1 deletions are larger deletions, spanning breakpoint (BP)1 and distal BP3 breakpoints, while type II deletions are smaller (approximately 500kb), spanning BP2 and BP3. Depending on the deletion type, behavioral differences have been reported in both PWS and AS patients. Type I patients have more severe phenotypes including delayed development and autistic features. Distinguishing between type I and type II deletions is useful in counseling PWS or AS patients. Type I and II deletions may be detected by evaluating the RP11-289D12 region on chromosome 15 with specific DNA probes.

 

A +dic(15) marker chromosome (an extra or supernumerary dicentric chromosome 15) is often familial and is usually consistent with a normal phenotype, but depending on its size, the marker can be associated with PWS or AS. Larger dic(15) are usually new mutations and are associated with mental retardation and mild dysmorphic features.

 

See Prader-Willi and Angelman Syndromes: Laboratory Approach to Diagnosis in Special Instructions for additional information.

Reference Values

An interpretive report will be provided.

Interpretation

Any individual with a normal signal pattern (2 signals) in each metaphase is considered negative for a deletion in the region tested by this probe (see Cautions).

 

Any patient with a FISH signal pattern indicating loss of the critical region will be reported as having a deletion of the region tested by this probe.

Clinical Reference

1. Butler MG, Bittel DC, Kibiryeva N, et al: Behavioral differences among subjects with Prader-Willi syndrome and type I and type II deletion and maternal disomy. Pediatrics 2004 Mar;113(3 pt 1):565-573

2. Varela MC, Kok F, Setian N, et al: Impact of molecular mechanisms, including deletion size, on Prader-Willi syndrome phenotype: study of 75 patients. Clin Genet 2005 Jan;67(1):45-52

3. Chai JH, Locke DP, Greally JM, et al: Identification of four highly conserved genes between breakpoint hotspots BP1 and BP2 of the Prader-Willi/Angelman syndromes deletion region that have undergone evolutionary transposition mediated by flanking duplicons. Am J Hum Genet 2003 Oct;73(4):898-925

Day(s) and Time(s) Performed

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

Analytic Time

7 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)

88274 w/modifier 52-Interphase in situ hybridization, <25 cells, each probe set (if appropriate)

88274-Interphase in situ hybridization, 25 to 99 cells, each probe set (if appropriate)

88275-Interphase in situ hybridization, 100 to 300 cells, each probe set (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
BP1F 15q Del Characterization, FISH In Process

 

Result ID Test Result Name Result LOINC Value
51869 Result Summary 50397-9
51871 Interpretation In Process
54541 Result No LOINC Needed
CG675 Reason For Referral 42349-1
CG676 Specimen 31208-2
51872 Source 31208-2
51873 Method 49549-9
51870 Additional Information 48767-8
53872 Disclaimer 62364-5
51874 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 form (if fetal specimen is sent) in Special Instructions (Only for products of conception or stillbirth specimen).

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

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