Non-invasive prenatal testing (NIPT), which is also known as cell-free DNA screening has been available (mainly in the private sector) in the UK since 2012. It involves a maternal blood test. The blood sample is sent to a laboratory and cell-free DNA material is extracted and analysed. Most of the DNA comes from the mother but a small amount comes from the baby’s placenta.
It is important to know that NIPT does not give a yes/no answer about chromosomal conditions. However, large scale studies show that the test has a high detection rate for Down’s syndrome. So it is currently a very sensitive screening test for Down's syndrome, and it can also look for Edwards' and Patau's syndrome, though it is not as reliable for these two conditions.
In 2014/15 a large evaluation study was carried out by Professor Lyn Chitty and her RAPID (Reliable Accurate Prenatal non-Invasive Diagnosis) project team. The team set out to provide information on how NIPT might be implemented into the NHS in a fair and affordable way. Prof Chitty reported their findings to the UK National Screening Committee in June 2015. After a detailed review of the international evidence and a public consultation, the UKNSC recommended that NIPT should be carefully implemented into the NHS as part of the current Fetal Anomaly Screening Programme, (to be offered to those women who have a screening result between 1 in 2 to 1 in 150). The Government accepted this advice. NIPT has been implemented in Wales. In Scotland it is hoped it will be available in the summer. There has been a delay in introducing NIPT into the NHS in England.
NIPT is widely available in the private sector.
Individual clinicians and private clinics are offering NIPT provided by a number of different laboratories, based here and overseas. There is no ‘direct to consumer’ testing available; it must be done via a health care professional. You can find out more about the labs doing the analysis below. They all claim high detection rates but some differ in the way they analyse the cfDNA. One way to check their claims is to look at the published data* they have on their test performance. You should be able to find this on their websites.
NIPT can be performed from 10 weeks of pregnancy. Before this it is difficult to collect enough cell-free DNA (cfDNA) from the blood sample. Even after 10 weeks there is a chance that they will not be able to collect enough cfDNA to provide a result. This can happen in about 3% of cases. Women who are significantly overweight have been found to be at higher risk of being in this 3%. Most providers will do a second test for free if this happens.
Results usually take a week to 10 days to come back from the laboratory. Remember NIPT does not give a yes/no answer; it gives a probability. If the result is reported as 'low chance' or 'very unlikely to be affected’, it is extremely unlikely that the baby has the condition. If the test result given is 'high chance' or ‘likely to be affected’ you will be offered a CVS or amniocentesis to give a definite diagnosis. It is important to realise that in this case the CVS or amniocentesis will most often confirm that the baby has Down's syndrome.
Our research suggests that costs for NIPT range from £350 to £550. If a provider is charging significantly more than £500, ask what the fee includes. Most clinics will include an ultrasound scan in the cost. If you are interested in having the test at a private clinic, make sure you check that they have a clear link with an NHS unit, so that there is a co-ordinated care pathway in place if you were to have a worrying test result.
Some private clinics are offering NIPT for sex chromosome and other conditions and even ‘micro deletions’ (when small pieces of genetic information are missing). We would advise you to think very carefully before agreeing to be tested for other conditions. The evidence is not so clear on how good NIPT is for these and sometimes you might be given information that leads to great uncertainty. Please feel able to call us on the helpline to talk this through or get expert advice from a clinical geneticist or genetic counsellor.
*to be of the highest quality, test performance data should be published in a peer reviewed scientific journal and should report pregnancy outcomes from studies involving 1000s of women.
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