Spinal Muscular Atrophy – Prenatal (Amniotic Fluid or Chorionic Villus)

Testing Laboratory

Department

Diagnostic Genetics

Delphic Registration Code (Alpha Code)

DGEN

Test Code (Numeric Code)

4218

Laboratory Handling

Registration

Place the sample into the box labelled DGEN on the shelf next to the dumbwaiter.

Sample Stability

Specimens to be kept at room temperature (>8 Degrees Celsius to <24 Degrees Celsius) and sent to LabPlus urgently.

Associated Tests

• Rapid Aneuploidy Screen, QF-PCR – Prenatal (Amniotic Fluid or Chorionic Villus)

Synonyms

Kugelberg-Welander Disease, Werdnig-Hoffman Disease, SMA, Spinal Muscular Atrophy

Turnaround Time

5 days

If the sample has to be cultured the turnaround time may vary depending on sample size, gestational age and cell growth rate: 14-21 days.

Specimen Type

• Amniotic Fluid
• Chorionic Villus (CVS)

Specimen Requirements

Tube/Container Type:

Preferred

• Specimen Container

Preferred Sample Volume (ml)

20

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• N/A

Additional Specimen Information

Amniotic Fluid (AF)- 20 mL of amniotic fluid collected aseptically into a sterile universal container (available on request from the Cytogenetics Laboratory).

Chorionic Villus (CVS): 20 mg of clean chorionic villi collected aseptically into a sterile container containing transport medium (containers and transport medium available on request from the Cytogenetics Laboratory). Send as soon as possible, as delays may affect cell growth.

Accompanying 4mL EDTA Maternal blood is ALWAYS required.

Aliquot Instructions

Transport to Lab

Ambient (8 - 24 degrees Celsius)

Additional Referral/Aliquot Information

Diagnostic referrals accepted from Specialist Services
Predictive testing accepted from Genetic Services.

Genetic Health Service NZ can be contacted on 0800 476 123.

The specialty of the referring clinician and the clinical presentation must be provided. Failure to provide the information required may delay testing.

Test Method

The Multiplex Ligation-dependent Probe Amplification (MLPA) kit P021-B1 SMA from MRC-Holland is used to detect copy number of exons 7 and 8 of SMN1 and SMN2, at region 5q13.2. Testing is performed alongside negative and positive controls. Analysis is performed using Coffalyser.Net.

Reference sequence: SMN1 - NM_000344.4, NP_000335.1 and SMN2 - NM_017411.4, NP_059107.1.

Limitations / Interference

The assay cannot detect point mutations, nor can it discriminate between 2 copies of SMN1 on the same chromosome versus 2 copies on separate chromosomes.

Uncertainty of Measurement

Please contact the Diagnostic Genetics Pathologist at dgen@adhb.govt.nz to discuss sources of test uncertainty, which include, but are not limited to, measurement uncertainty (MU) and biological variation.

Contact Information