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Test ID: STSF Steroid Sulfatase Deficiency, Xp22.3 Deletion, FISH

Useful For

Establishing a diagnosis of X-linked ichthyosis syndrome

            

Detecting cryptic rearrangements involving Xp22.3 that are not demonstrated by conventional chromosome studies

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
_IL25 Interphases, <25 No, (Bill Only) No
_I099 Interphases, 25-99 No, (Bill Only) No
_I300 Interphases, ≥100 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.

 

Method Name

Fluorescence In Situ Hybridization (FISH)

Reporting Name

STS, Xp22.3, FISH

Specimen Type

Varies


Specimen Required


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: 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.

 

Submit only 1 of the following specimens:

 

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: Autopsy

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. 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.

 

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 (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: Fixed cell pellet

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

Specimen Volume: Entire specimen

 

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 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.

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

Specimen Stability Information

Specimen Type Temperature Time
Varies Refrigerated (preferred)
  Ambient 

Clinical Information

This test is appropriate in individuals with clinical features suggestive of X-linked ichthyosis and carrier testing for women with a family history of X-linked ichthyosis.

                         

Steroid sulfatase deficiency syndrome is associated with a deletion of the STS gene on the short arm of X chromosome (Xp22.3). The syndrome is an X-linked form of ichthyosis, which is a group of cutaneous disorders characterized by increased or abnormal keratinization. The phenotype is variable, with affected males presenting with dry and scaly skin, sparse hair, and conical teeth.

 

Steroid sulfatase catalyzes the conversion of sulfated steroid precursors to estrogens during pregnancy. Prenatal specimens may be tested in cases where maternal serum screening has identified low or absent levels of unconjugated estriol (UE3). Female relatives of affected males carry the deletion and should be tested if an affected male has been identified.

Reference Values

An interpretive report will be provided.

Interpretation

Any individual with a normal signal pattern (1 signal on the X homolog) in each metaphase is considered negative for a deletion in the region tested by this probe.

 

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

Clinical Reference

1. Valdes-Flores M, Kofman-Alfaro SH, Jimenez-Vaca AL, Cuevas-Covarrubias SA: Carrier identification by FISH analysis in isolated cases of X-linked ichthyosis. Am J Med Genet 2001;102,146-148

2. Hernandez-Martin A, Gonzalez-Sarmiento R, De Unamuno P: X-linked ichthyosis: an update. Br J Dermatol 1999:141:617-627

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

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)

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
STSF STS, Xp22.3, FISH In Process

 

Result ID Test Result Name Result LOINC Value
51830 Result Summary 50397-9
51832 Interpretation In Process
54535 Result No LOINC Needed
CG664 Reason For Referral 42349-1
CG665 Specimen 31208-2
51833 Source 31208-2
51834 Method 49549-9
51831 Additional Information 48767-8
55270 Disclaimer 62364-5
51835 Released By No LOINC Needed
Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

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