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Test Code TwinZyg Twin Zygosity Testing

Clinical System Name

Twin Zygosity Testing


Zygosity Testing

Fetal Zygosity

Mono/Dizygotic Differentiation

Newborn Zygosity

Zygosity, Twin Pre/Postnatal

Sample Requirements

Specimen: Whole Blood

Container(s): From each twin: Lavender/EDTA, Yellow/ACD A, or Yellow/ACD B

Preferred Vol: From each twin: 3 mL

Minimum Vol: From each twin: 2 mL


Specimen: Buccal Swab

Container(s): From each twin: Sterile Screw-Capped Container

Preferred Vol: From each twin: 2 Buccal Swabs

Minimum Vol: From each twin: 2 Buccal Swabs


Note: Collect TWO buccal swabs from each twin. Label the container(s) appropriately.

1-3 mL whole blood in Lavender/EDTA  or Yellow/ACD A or B also acceptable. Blood must be collected from BOTH twins.

Processing Instructions

Reject due to: Frozen specimens.

Spin: N

Aliquot: N

Temp: 2 - 4 C

Storage location: Deliver swabs in container(s) to CPA refrigerator, Send Outs rack. Do not spin blood, deliver to CPA refrigerator, Send Outs rack.


Off-site collection: Do not spin whole blood. Refrigerate swabs or whole blood.


Specimen Type Temperature Time
Whole Blood or Buccal Swab Room temp

72 h

  Refrigerated 1 w




STAT Performed TAT
N Varies 5 - 10 d


Performing Laboratory

ARUP Laboratories

500 Chipeta Way
Salt Lake City, UT 84108-1221


Phone Number: (800) 522-2787


Department: Send Outs


Phone Number: (206) 987-2563


Reference Range

Monozygotic Twins Greater than 99% certainty (all markers match)
Dizygotic Twins 99% certainty (two or more markers do not match)



Method: Polymerase Chain Reaction/Fragment Analysis

Analytical Volume: 1 mL Whole Blood or 2 Buccal Brushes


Special Instructions

Links to:





Send Out Instructions

Reference Test Name: Twin Zygosity Testing
Reference Test Number:



Send out Monday - Friday with the ARUP courier.