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HelpTest ID MULT Zygosity Testing (Multiple Births)
Useful For
Determining genetic risk for an individual whose twin or triplet is affected with a genetic disorder for which a specific genetic test is not available (or such testing is uninformative)
Assessment of risks prenatally when 1 fetus of multiples is known to be affected by a specific disorder
Organ or bone marrow transplantation compatibility testing
Familial or parental interest
Genetics Test Information
DNA from twins and their parents is used to determine if the twins are identical (monozygotic) or fraternal (dizygotic).
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| CULFB | Fibroblast Culture for Genetic Test | Yes | No |
| CULAF | Amniotic Fluid Culture/Genetic Test | Yes | No |
| _STR1 | Comp Analysis using STR (Bill only) | No | No |
| _STR2 | Add'l comp analysis w/STR (Bill Only) | No | No |
Testing Algorithm
For prenatal specimens only: If amniotic fluid (nonconfluent cultured cells) is received, amniotic fluid culture/genetic test will be added and charged separately. If chorionic villus specimen (nonconfluent cultured cells) is received, fibroblast culture for genetic test will be added and charged separately.
Special Instructions
Method Name
Polymerase chain reaction (PCR)/microsatellite markers are used to provide a genotype for multiples and their parents to determine if siblings are monozygotic twins.
Reporting Name
Zygosity Testing (Multiple Births)Specimen Type
VariesShipping Instructions
Specimen preferred to arrive within 96 hours of draw.
Necessary Information
A blood specimen from both parents, in addition to a specimen from each multiple, is required. Each specimen will be charged separately.
Specimen Required
Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.
Submit only 1 of the following specimens:
Specimen Type: Whole blood
Container/Tube: Lavender top (EDTA) or yellow top (ACD)
Specimen Volume: 3 mL
Collection Instructions:
1. Invert several times to mix blood.
2. Send specimen in original tube.
Specimen Stability Information: Ambient (preferred)/Refrigerated
Due to the complexity of prenatal testing, consultation with the laboratory is required for all prenatal testing. Prenatal specimens can be sent Monday through Thursday and must be received by 5 p.m. CST on Friday in order to be processed appropriately. All prenatal specimens must be accompanied by a maternal blood specimen. Order MATCC / Maternal Cell Contamination, Molecular Analysis on both the prenatal and the maternal specimens.
Specimen Type: Amniotic fluid
Container/Tube: Amniotic fluid container
Specimen Volume: 20 mL
Specimen Stability Information: Refrigerated (preferred)/Ambient
Specimen Type: Chorionic villi
Container/Tube: 15-mL tube containing 15 mL of transport media
Specimen Volume: 20 mg
Specimen Stability Information: Refrigerated
Acceptable:
Specimen Type: Confluent cultured cells
Container/Tube: T-25 flask
Specimen Volume: 2 flasks
Collection Instructions: Submit confluent cultured cells from another laboratory.
Specimen Stability Information: Ambient (preferred)/Refrigerated
Specimen Minimum Volume
Blood: 0.5 mL
Amniotic Fluid: 10 mL
Chorionic Villi: 5 mg
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Varies | Varies | |
Reference Values
An interpretive report will be provided.
Day(s) and Time(s) Performed
Monday; 10 a.m.
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics 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
81265 Comparative analysis using Short Tandem Repeat (STR) markers; patient and comparative specimen (eg, pre-transplant recipient and donor germline testing, post-transplant non-hematopoietic recipient germline [eg, buccal swab or other germline tissue sample] and donor testing, twin zygosity testing or maternal cell contamination of fetal cells
Fibroblast Culture for Genetic Test
88233-Tissue culture, skin or solid tissue biopsy (if appropriate)
88240-Cryopreservation (if appropriate)
Amniotic Fluid Culture/Genetic Test
88235-Tissue culture for amniotic fluid (if appropriate)
88240-Cryopreservation (if appropriate)
Added as needed:
81266 each additional specimen (eg additional cord blood donor, additional fetal samples from different cultures, or additional zygosity in multiple birth pregnancies)
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| MULT | Zygosity Testing (Multiple Births) | In Process |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 53322 | Result Summary | 50397-9 |
| 53323 | Result | 69548-6 |
| 53324 | Interpretation | 69965-2 |
| 53349 | Reason for Referral | 42349-1 |
| 53325 | Specimen | 31208-2 |
| 53326 | Source | 31208-2 |
| 53327 | Method | 49549-9 |
| 53328 | Released By | 18771-6 |
Forms
1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing (Spanish) (T826)
2. Molecular Genetics: Congenital Inherited Diseases Patient Information (T521) in Special Instructions