Twin Zygosity Study

TEST: 176548
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CPT: 81265
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Synonyms

  • Dizygosity Study
  • Fraternal Twin Test
  • Identical Twin Test
  • Monozygotic and Dizygotic Twin Diagnosis
  • Zygosity Studies

Special Instructions

Include race/ethnicity and gender of the twins. Samples being tested at the request of a clinical account must have a completed test request form. If this study is collected for legal purposes, appointments and paternity kits are required. Specimens for legal testing must be collected with chain-of-custody paper work. To receive a complete paternity kit, blood or buccal swab, or for an appointment for legal testing, telephone 800-742-3844.

Expected Turnaround Time

3 - 7 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Specimen Requirements

Specimen

Whole blood or buccal swabs; other samples, such as amniotic fluid, cultured cells, and tissue specimens, may be used.

Volume

3 mL whole blood or four buccal swabs; other tissue as available.

Container

Lavender-top (EDTA) tube or four buccal swabs in a sealed envelope (buccal swab kit). Amniotic fluid and tissue in appropriate transport container. When submitting buccal swabs, please use a buccal swab kit provided by LabCorp. To obtain the buccal swab kit, please telephone 800-533-1037.

Storage Instructions

Maintain blood specimen at room temperature and keep dry.

Causes for Rejection

Improperly labeled specimen; improperly filled out client authorization/chain-of-custody form; insufficient amount of DNA on buccal swabs

Test Details

Use

Provide evidence that twins are monozygotic versus dizygotic. This test may be used for legal purposes, obstetric management, as part of a transplant evaluation, and for other purposes.

Limitations

The probability that twins are monozygotic is a statistical assessment and, as such, even though the twins have identical results and a high probability of being monozygotic, there is always a small probability that the twins are dizygotic. This chance is reflected in the probability provided. The statistical assessment can be improved by the submission of the parents of the twins.

This test was developed, and its performance characteristics determined, by LabCorp. This test has not been cleared or approved by the US Food and Drug Administration (FDA). The FDA has determined that such clearance is not necessary.

Methodology

DNA analysis by polymerase chain reaction (PCR)

Reference Interval

If the twins do not have identical results, the report will conclude the twins are dizygotic. If the twins have identical results, a statistical assessment of the probability they are monozygotic is provided. The monozygotic probability assessment will typically exceed 99.0%.

References

Smith SM, Penrose LS. Monozygotic and dizygotic twin diagnosis. Ann Hum Genet. 1955 Jun; 19(4):273-289. 14388534
Vogel F, Motulsky AG. Appendix 5: Diagnosis of zygosity. Human Genetics: Problems and Approaches. 2nd ed. New York, NY: Springer-Verlag;1986:669-676.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
176548 Twin Zygosity Study 176530 D3S1358 N/A
176548 Twin Zygosity Study 176531 D7S820 N/A
176548 Twin Zygosity Study 176532 Amelogenin N/A
176548 Twin Zygosity Study 176533 vWA N/A
176548 Twin Zygosity Study 176534 FGA N/A
176548 Twin Zygosity Study 176535 D8S1179 N/A
176548 Twin Zygosity Study 176536 D21S11 N/A
176548 Twin Zygosity Study 176594 D18S51 N/A
176548 Twin Zygosity Study 176595 D5S818 N/A
176548 Twin Zygosity Study 176596 D13S317 N/A
176548 Twin Zygosity Study 176597 D16S539 N/A
176548 Twin Zygosity Study 176598 TH01 N/A
176548 Twin Zygosity Study 176599 TPOX N/A
176548 Twin Zygosity Study 176600 CSF1PO N/A
176548 Twin Zygosity Study 176603 QC N/A

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