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Fetal Genotyping for Red Cell Antigen - Jka/Jkb

Kidd, jka, jkb, Kidd antigen genotyping

Test Codes

Blood Center of Wisconsin: BCW3862, Order as a Miscellaneous Send Out.

Department

Send Outs

Specimen Collection Criteria

Collect: Fetal specimen as well as maternal and paternal specimens, as described below:

• Fetal: 7-15 mL amniotic fluid, cultured amniotic cells (2.0x10⁶ cells minimum), or Chorionic Villus specimen (CVS).
• Maternal/Paternal: Two Lavender-top EDTA tubes from each the mother and the father.

Send both maternal and paternal whole blood with the fetal sample to ensure that the antigen in question can be detected in this assay. The maternal sample is also used to rule out maternal contamination in the fetal sample. Include serologic typing results for both parents on the test requisition.

Physician Office/Draw Specimen Preparation

• Maintain fetal specimens at room temperature (20-26°C or 68-78.8°F) prior to transport.
• Do not centrifuge maternal and paternal specimens. Maintain whole blood at room temperature (20-26°C or 68-78.8°F) prior to transport.

Preparation for Courier Transport

Transport: Fetal specimen [15 mL amniotic fluid (Minimum: 7.0 mL), cultured amniotic cells (Minimum: 2.0x10⁶ cells), or chorionic villus sample] and maternal and paternal specimens [10 mL whole blood (Minimum: 2.0 mL) from both the mother and the father], at room temperature (20-26°C or 68-78.8°F).

Rejection Criteria

Specimens not collected and processed as indicated.

In-Lab Processing

• Maintain fetal specimens at room temperature (20-26°C or 68-78.8°F) prior to transport.
• Do not centrifuge maternal and paternal specimens. Maintain whole blood at room temperature (20-26°C or 68-78.8°F) prior to transport.

Transport: Fetal specimen [15 mL amniotic fluid (Minimum: 7.0 mL), cultured amniotic cells (Minimum: 2.0x10⁶ cells), or chorionic villus sample] and maternal and paternal specimens [10 mL whole blood (Minimum: 2.0 mL) from both the mother and the father], at room temperature (20-26°C or 68-78.8°F).

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 7 days
Refrigerated (2-8°C or 36-46°F): 14 days
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.

Laboratory

Sent to Blood Center of Southeastern Wisconsin, Milwaukee, WI.

Performed

Monday – Friday.
Results available in 5-7 days. 

Reference Range

By report.

Test Methodology

• Allele-specific Polymerase Chain Reaction (PCR).
• Parental genotyping to confirm that the antigen in question is detectable at the DNA level and screening the fetal sample for maternal contamination is included.

Interpretation

Hemolytic disease of the newborn (HDN) results from sensitization of the mother's immune system to foreign antigens present on the red cells of the fetus. Many red cell antigen systems have been associated with HDN when incompatibilities exist between the mother and fetus. When a pregnant woman presents with an antibody titre to a blood group antigen, it is important to know the antigen status of the fetus, especially if the father's antigen type is unknown or he is heterozygous for the antigen system in question. Prenatal genotyping can provide that answer, allowing for appropriate management of fetuses at risk, while preventing invasive and expensive monitoring and therapies for fetuses not at risk.

Clinical Utility

This assay aids in the management of pregnancy with no history of HDN but with elevated anti-red cell antigen antibodies or when a previous pregnancy was complicated by HDN with unknown or heterozygous paternal blood type.

CPT Codes

81479, 86905x2.

Contacts

Last Updated

9/11/2023