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Test Code HLX GC Chromosome Analysis Constitutional CASE 22q11.2 Deletion, Velocardiofacial and DiGeorge Syndromes, FISH

Performing Laboratory

Northwell Health Laboratories


Metaphase Fluorescence In Situ Hybridization (FISH) with DNA Probes for DiGeorge Chromosome Region (D22S75) of Chromosome 22 (22q11.2)

A control probe for 22q13 is also included in the hybridization.

Specimen Requirements

Please provide a reason for referral with each specimen. The laboratory will not delay or reject testing if this information is not provided, but appropriate testing and interpretation may be compromised.


Submit only 1 of the following specimens:




Container/Tube:  Green-top (sodium heparin) tube(s) - Clotted blood is not acceptable.

Specimen:  5 mL to 10 mL (minimum volume:  2 mL) of sodium heparin whole blood.

Transport Temperature:  Room Temperature

Collection Instructions:  Invert several times to mix blood. Other anticoagulants are not recommended and are harmful to the viability of the cells. Label vial with patient’s name and laboratory control number. Forward promptly. Specimen cannot be frozen.



Amniotic Fluid

Optimum timing for specimen collection is during 16th to 18th weeks of gestation, but specimens collected at other weeks of gestation are also accepted. Draw 20 mL to 25 mL of amniotic fluid in a sterile syringe (we strongly recommend Pharmaseal amniocentesis tray distributed by Cardinal Health Company. Discard first 2 mL of amniotic fluid, and send remainder to laboratory. When using a Pharmaseal Amniocentesis Kit, transfer the amniotic fluid into provided transport containers. If Pharmaseal amniocentesis tray is not available, use a Becton-Dickinson syringe; and transport specimen as follows. Remove needle and transfer specimen to 2 screw-capped, sterile 15-mL centrifuge tubes. Place the tubes in a Styrofoam® container. Fill remaining space with packing material. Unavoidably, about 1% to 2% of mailed-in specimens are not viable. Bloody specimens are undesirable. If the specimen does not grow in culture, you will be notified within 7 days of receipt. Label container with patient’s name and laboratory control number. Send specimen refrigerated. Specimen cannot be frozen. Results will be reported and also telephoned or faxed, if requested.


Chorionic Villus

Obtain 20 mg to 30 mg (minimum volume:  5 mg) of a chorionic villus specimen (CVS) by transabdominal or transcervical method. Transfer the CVS to a Petri dish containing transport medium. Using a stereomicroscope and sterile forceps, assess the quality and quantity of villi; and remove any blood clots and maternal decidua. Transfer the CVS by using sterile technique to 1 or 2 15-mL centrifuge tube(s) with 15 mL of transport medium. Label the centrifuge tube(s) with patient’s name and laboratory control number. Send specimen refrigerated. Specimen cannot be frozen.

Skin Biopsy

Wash biopsy site with an antiseptic soap (eg, pHisoHex®). Thoroughly rinse area with sterile water. Do not use alcohol or iodine preparations. A local anesthetic may be used. Biopsy specimens are best taken by punch biopsy to include full thickness of dermis. Biopsy should be 4 mm in diameter. Aseptically place biopsy in a screw-capped, sterile container with sterile Hank’s balanced salt solution, Ringer’s solution, or normal saline. Do not handle with hands. Label container with patient’s name and laboratory control number. Send specimen refrigerated. Specimen cannot be frozen.

Reference Values

In normal individuals, each metaphase should show a normal signal pattern. Individuals with a deletion should show an abnormal signal pattern in each metaphase.

Test Classification and CPT Coding

88271 x 2 - DNA probe, each

88273 x 2 - chromosomal in situ hybridization

88291 - interpretation and report

Day(s) and Time(s) Performed

Monday through Sunday