Polymerase Chain Reaction/Fragment Analysis
From each twin: Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B). Also acceptable: Buccal brushes.
From each twin: Transport 3 mL whole blood (Min: 1 mL) Also acceptable: 2 buccal brushes.
Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics: Monozygotic twins originate from a single fertilized ovum dividing into two embryos, while dizygotic twins result from ovulation of two eggs during a single menstrual cycle.
Incidence: Twins are delivered 1 in 77 Caucasian births; 70 percent are dizygotic and 30 percent are monozygotic.
Cause: Dizygotic twinning is related to increased levels of maternal follicle stimulating hormone.
Clinical Sensitivity: 99 percent.
Methodology: PCR followed by capillary electrophoresis; specimens are analyzed using 15 autosomal short tandem repeat markers (D8S11 79, D21S11, D7S820, CSF1PO, D3S1358, THO1, D13S317, D16S539, D2S1338, D19S433, vWa, TPOX, D18S51, D5S818 and FGA) and one gender marker (Amelogenin).
Analytic Sensitivity: 99 percent.
Limitations: Diagnostic errors can occur due to rare sequence variations.
Laboratory Developed Test (LDT)
Results from both twins will be compared and reported; therefore a test must be ordered for and sample submitted from each individual.
|Component Test Code*||Component Chart Name||LOINC|
|0050547||Twin Zygosity Testing Interpretation|
|2001383||Twin Zygosity Testing Specimen|
- Fetal Zygosity
- Mono/Dizygotic Differentiation
- Newborn Zygosity
- Zygosity, Twin Pre/Postnatal