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Rapid Aneuploidy Detection (RAD) - Saskatoon

Discipline

Genetics and Genomics

Overview

Description

Ordering recommendations

  • Rapid Aneuploidy Detection (RAD) detects the most common fetal autosomal aneuploidies (trisomy 13, trisomy 18 and trisomy 21) as well as the sex chromosome.
  • Optimal timing for direct amniotic fluid specimen collection is between 14 to 18 weeks of gestation, but specimens collected at later gestation are also accepted
  • RAD testing may be ordered on tissues, such as fetal umbilical cords and products of conception (POC). Fetal parts of POC must be identified by a pathologist before performing the test.
  • RAD testing may be ordered on blood specimens collected from newborns
  • If an abnormal RAD result is detected on amniotic fluid, please note:
    • No irreversible medical decisions about a pregnancy should be made based solely on results of RAD testing.
    • This result should be evaluated in conjunction with chromosome analysis, ultrasound and other clinical findings.
    • Genetic counselling is recommended if not already sought.

Ordering requirements

Specimen Information

Specimen types accepted

  • Amniotic fluid - avoid bloody sampling of direct amniotic fluid to reduce error of maternal cell contamination
  • Peripheral blood or Cord blood
  • Tissues, such as fetal umbilical cord, or fetal parts identified from products of conception (POC) by a pathologist

Specimen collection container

Collection procedure

  • Specimen must be accompanied by a completed test requisition, signed by physician
  • Failure to include relevant patient information may result in test results being delayed or discontinued
  • If collecting peripheral blood, invert tube several times to mix

Required volume

  • Direct amniotic fluid optimal volume: 15-20 ml divided between two tubes
  • Optimal volume of peripheral or cord blood: 4 - 7 mL
  • Minimum volume for pediatric patient: 1 mL of peripheral blood or cord blood
  • Approximately 2.5 cm of cord from placental end
  • Approximately 0.5 cm x 0.5 cm of fetal tissue, identified by a pathologist
  • Skin biopsy punch (approximately 0.5 cm x 0.5 cm)

Transport and stability

  • Specimens are to be kept and delivered at room temperature
  • Do not freeze specimen or expose to extreme heat
  • Do not formalin fix the tissue
  • If storing overnight, keep refrigerated at 4 - 8°C

Rejection criteria

Testing Information

Relevant clinical history

Patient history

  • Positive maternal serum screen
  • Ultrasound anomalies
  • Advanced maternal age (> 40 years)
  • Other relevant indications
  • Please refer to the requisition for details

Performance

Methodology

  • RAD testing with extracted DNA is performed using the Yourgene Elucigene® QST*Rplusv2 kit, which allows rapid detection of the most common fetal autosomal aneuploidies (trisomy 13, trisomy 18 and trisomy 21) as well as the sex chromosome using Quantitative Fluorescent Polymerase Chain Reaction (QF-PCR).

Days/times performed

Availability

  • Specimens are received in the RUH Genomics Laboratory weekdays from 8:00 a.m. to 5:00 p.m.
  • There is a technologist on call Saturday, Sunday and statutory holidays from 8:30 a.m. to 5:00 p.m. for urgent specimens only. This person can be reached through Royal University Hospital Switchboard (655-1000)

Maximum laboratory time

Result reporting 

  • Turnaround time: 5 business days
  • Reflex confirmatory karyotype testing may be performed after an abnormal RAD result, depending sample availability.
  • A referral to Medical Genetics is required to request Chromosomal Microarray based on indication and/or Rapid Aneuploidy Detection (RAD) results.

Specimen retention time

  • If DNA banking is requested, the DNA will be extracted and sent to RRPL for storage as their banking policy.

Last Updated: April 2, 2024