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Illumina Test

The Illumina Test is a non-invasive prenatal screening test (NIPT), to determine the risk of Down’s Syndrome in an unborn child. We are one of few centres in the UK now offering the Illumina test for screening for Down's Syndrome. The screening involves a simple blood test taken from the mother during pregnancy (from 10 weeks onwards) which strongly predicts some of the most common chromosomal abnormalities such as Trisomy 21 (Down's Syndrome), Trisomy 18 (Edwards Syndrome), Trisomy 13 (Patau Syndrome).

 

The Illumina test has been clinically proven to have detection rates of over 99% for Down's Syndrome, and can be performed at no risk to the baby. All that is required is a blood sample from the mother, which is taken from 10 weeks gestation. This is a much-preferred option than traditional, stressful invasive testing such as chorionic villous sampling (CVS) and amniocentesis.

 

Chromosomal conditions can occur in any pregnancy, and our Illumina tests are able to provide you with peace of mind about the health of your baby and its likelihood of developing the most common chromosomal conditions. The Illumina test is far more accurate than traditional screening and offers lower false positive rates.

 

At Women’s Health Dulwich, we work closely with the UK’s oldest and largest private laboratory. Typically, the Harmony test results are available in less than 7 working days. If you're from Dulwich or the surrounding area, and you are looking for a reliable, trustworthy clinic for your prenatal screening, contact us today. 

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About the Illumina Test

How accurate is NIPT?

 

Non-invasive prenatal testing (NIPT) is a screening test – it is a test for women who are unlikely to have a baby with a chromosome condition. It is much more accurate than first trimester blood screening and ultrasound tests. This has reduced the need for invasive tests such as chorionic villus sampling (CVS) or amniocentesis, although these will still be required to confirm a high probability result.

 

NIPT screening for trisomy 21, 18 and 13 – the most common chromosome conditions – provides the highest accuracy. Screening for other syndromes or for fetal sex is reasonably reliable; however, it is not as accurate as the screening for trisomy 21, 18 and 13.

 

Who should have NIPT?

 

Chromosomal conditions like Down syndrome (trisomy 21) do not typically run in families and can happen in any pregnancy. Although the chance of having a baby with Down syndrome increases with age, most babies with Down syndrome are born to women under 35.2

 

You must be at least 10 weeks pregnant for this test. Patients who have received bone marrow or organ transplants, or those who have metastatic cancer are not eligible for the test.

 

How does NIPT work?

 

There are small fragments of DNA in the mother’s blood that have come from both the mother and the placenta. This is a normal process.

 

TDL Genetics uses an NIPT assay called Veriseq v2, manufactured by Illumina and processed in our London laboratory. The assay analyses the proportions of the DNA fragments that come from specific chromosomes.

 

If a particular proportion is too high or too low, this indicates that there may be a chromosome condition involving the placenta and, potentially, the developing baby.

 

What the NIPT report will include, and how you will receive your test results

 

Your sample is checked to see if there is sufficient DNA from the developing pregnancy to provide a reliable result. Then, for each condition included on the request form, the report will indicate whether there is a low or high probability of the condition being present.

 

Results will be sent to your healthcare provider in 5 business days.

 

Your healthcare provider will discuss the report with you and let you know if any other investigations are recommended. In your initial consultation, prior to the test being ordered, we strongly advise that you discuss what you would do

with the possible results.

 

If your report indicates a high probability of a chromosome condition being present, a CVS or amniocentesis procedure can be arranged by your doctor to obtain a definitive result.

 

Does a low probability result mean that the baby does not have Down Syndrome?

 

No, any screening test carries a chance of a ‘false negative’ however the chance of this happening with NIPT is much lower than with conventional screening for Down syndrome and other chromosome conditions.

 

If I have a high probability result, does that mean that the baby’s chromosomes are abnormal?

 

No, not necessarily. It means that there is a higher chance that your baby may have a chromosome condition, and you will be offered the option of amniocentesis to assess the chromosomes directly. You will be offered support and counselling to help you reach that decision.

What if I have twins?

 

This test can also be applied to twin pregnancies but is not suitable in the case of a vanishing or demised twin.

The sex of twins will be reported as one result. If male, one or both of the twins will be male. If female, both twins will be female.

 

Will I always get a result?

 

Two out of 100 women will require a repeat test. Patients will not be charged if we are unable to obtain a result.

On rare occasions, it is not possible to issue an NIPT result. This is usually due to the complex biology of pregnancy rather than a failure of the test method.

If NIPT cannot provide an assessment for the three most common chromosome conditions (trisomy 21, 18 and 13) after one collection of a blood sample (or two, if recommended by the laboratory), you will not be charged.

 

Does NIPT have any limitations?

 

The NIPT assay used by TDL Genetics – VeriSeq NIPT Solution v2 – is not validated for use in pregnancies

 

with more than two fetuses, nor in cases of fetal demise, mosaicism, partial chromosome aneuploidy, triploidy, translocations, maternal aneuploidy, transplant or malignancy. VeriSeq NIPT Solution v2 does not detect neural tube defects. Certain rare biological conditions may also affect the accuracy of the test.

 

For twin pregnancies, HIGH PROBABILITY test results apply to at least one fetus; male test results apply to one or both fetuses; female test results apply to both fetuses.

Due to the limitations of the test, inaccurate results are possible.

 

A LOW PROBABILITY result does not guarantee that a fetus is unaffected by a chromosomal or genetic condition. Some fetuses without a trisomy or chromosomes anomaly may have HIGH PROBABILITY results. In cases of HIGH PROBABILITY results and/or other clinical indications of a chromosomal condition, confirmatory testing is necessary for diagnosis.

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