Galactosemia Mutation Analysis

Test Code

16613

CPT Codes
81401<br />

Physician Attestation of Informed Consent

This germline genetic test requires physician attestation that patient consent has been received if ordering medical facility is located in AK, DE, FL, GA, IA, MA, MN, NV, NJ, NY, OR, SD or VT or test is performed in MA.

Preferred Specimen

5 mL whole blood collected in an EDTA (lavender-top) tube

Minimum Volume

3 mL whole blood • 10 mL amniotic fluid • 10 mg chorionic villi

Other Acceptable Specimens

Whole blood collected in: Sodium heparin (green-top) tube or ACD (yellow-top) tube • 10 mL amniotic fluid collected in a sterile plastic leak-proof container • 10 mg chorionic villi collected in a sterile tube filled with sterile culture media • Cultured cells collected in each of two separate sterile T-25 flasks, 75% confluent

Instructions

Do not hold specimen; forward to laboratory when specimen arrives.

Whole blood (preferred): Specimen stability is crucial. Store and ship room temperature immediately. Do not freeze.

For fetal testing:
1) Please call 1-866-GENE-INFO (1-866-436-3463) prior to submission; 2) Documentation of parental carrier status must be provided; 3) It is required that Maternal Cell Contamination Study, STR Analysis be ordered in conjunction with fetal testing. A separate tube of maternal blood (EDTA) is required for this test.

Amniotic fluid (acceptable): Normal collection procedure. Specimen stability is crucial. Store and ship at room temperature immediately. Do not refrigerate or freeze; forward to laboratory when sample arrives.

Amniocyte or Chorionic Villus (CVS) culture (acceptable): Two sterile T25 flasks, 75% confluent, filled with culture medium. Specimen stability is crucial. Store and ship at room temperature immediately. Do not refrigerate or freeze; forward to laboratory when cells arrive.

Dissected Chorionic Villus (CVS) biopsy (acceptable): 10-20 mg dissected chorionic villi collected in sterile tube, filled with sterile culture medium. Specimen stability is crucial. Store and ship at room temperature immediately. Do not refrigerate or freeze; forward to laboratory when sample arrives.

Transport Temperature

Room temperature

Specimen Stability

⁠⁠⁠⁠⁠⁠⁠Whole blood
Room temperature: 8 days
Refrigerated: 8 days
Frozen: Unacceptable

Amniotic fluid, chorionic villi, cultured cells
Room temperature: 48 hours
Refrigerated: Unacceptable
Frozen: Unacceptable

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Do not reject

Methodology
Polymerase Chain Reaction (PCR) • Single Nucleotidase Primer Extension

FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.

Setup Schedule

Set up: Tues; Report available: 8 days

Limitations

This test will detect more than 80% of the classic galactosemia mutations in the general U.S. population. Everyone has two copies of the GALT gene. An individual may have two normal copies (unaffected, non-carrier), two abnormal copies (affected with galactosemia) or one normal and one abnormal (galactosemia carrier). If mutations are not found, it does not mean that the risk of carrying or developing galactosemia is not present. It simply means that these specific mutations have not been found, although other mutations may be present.

Reference Range

See Laboratory Report

Clinical Significance

Galactosemia is an inborn error of metabolism for the sugar galactose. More than 95% of the galactosemia is due to mutations in the gene coding for the enzymes UPD galactosyl transferase (GALT). There are many false-positives on newborn screen tests due to enzyme instability and a frequent polymorphism called the Duarte variant in the GALT gene. DNA analysis is the preferred confirmation method.

Performing Laboratory

Quest Diagnostics Nichols Institute-San Juan Capistrano, CA

33608 Ortega Highway

San Juan Capistrano, CA 92675-2042

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.