TDL VeriSeq V2 Illumina NIPT in London

No — they are different tests from the same laboratory. TDL (The Doctors Laboratory) was the UK provider of the Harmony test for around a decade, from the distribution partnership announced in January 2013 until it withdrew the test in September 2023, at roughly two weeks’ notice. TDL VeriSeq V2 is the test it now runs in Harmony’s place.

What the two share is the laboratory, the London location and the clinical purpose: screening for Down’s, Edwards’ and Patau’s syndromes from a single maternal blood sample, with optional fetal sex determination. What differs is the technology underneath. Harmony used a targeted cell-free DNA method; VeriSeq V2 uses the Illumina VeriSeq NIPT Solution v2, a whole-genome sequencing assay.

If you were referred specifically for Harmony, this is the test TDL now runs in its place. Our Harmony test page explains the background, and Harmony test alternatives lists everything we now offer instead.

In the manufacturer’s validation of the VeriSeq NIPT Solution v2 assay, and excluding known mosaic cases, the basic screening analysis correctly classified 130 of 130 confirmed trisomy 21 samples, 41 of 41 trisomy 18 samples and 26 of 26 trisomy 13 samples. Sensitivity was above 99.

9 per cent for each, but with wide confidence intervals reflecting the small number of confirmed cases — 95% CI 97.1-100% for trisomy 21, 91.4-100% for trisomy 18 and 87.1-100% for trisomy 13. Specificity was 99.90 per cent for each, with six false-positive results in total, and 1.2 per cent of samples failed quality control at first pass (Pertile et al.

, Clinical Chemistry, 2021).

Validation cohorts are deliberately enriched with affected pregnancies, so those figures are best read as evidence that the assay works as intended rather than as the numbers you should expect personally. In routine populations, a systematic review and meta-analysis of cell-free DNA screening reported pooled detection rates of 99.3 per cent for trisomy 21 and 97.4 per cent for trisomies 18 and 13, with specificity of 99.9 per cent or above (Taylor-Phillips et al., BMJ Open, 2016).

Accuracy is not the same as certainty, and no NIPT is diagnostic. What determines the meaning of your own result is the positive predictive value, which also depends on your background chance — our NIPT PPV calculator illustrates this, and NIPT results explained covers the terminology.

Results usually reach us in 2-4 working days from the laboratory receiving your sample. TDL’s own wording is that results are ready in approximately 2-4 days, so treat this as a typical turnaround rather than a guarantee.

The main reason it is quick is geography. TDL’s genetics laboratory is in London, so your sample travels across the city by medical courier rather than by international freight — considerably faster than tests processed in the United States. The Illumina workflow itself is highly automated and, according to the manufacturer, goes from sample to report in approximately 26 hours once a run begins.

If a sample needs repeating — most often because there was not enough placental DNA in the first draw — a second sample adds a few days. We contact you as soon as a clinician has reviewed and authorised your result.

£540 for the test together with an expert ultrasound scan at our London clinic — the scan is part of every NIPT we offer. That is the same price as our PrenatalSAFE package, which screens for the same three conditions.

Because the two are priced the same and cover the same conditions, the choice between them is not about money. TDL VeriSeq V2 is the one to pick if you were referred for Harmony or want the same TDL laboratory; PrenatalSAFE is our default otherwise, and it is the option validated for vanishing twin pregnancies.

The £540 package covers the scan, the blood draw, the laboratory fee, clinician review of your result and a telephone call to explain what it means. Optional fetal sex determination is included rather than charged as an extra. You can see how this compares with our other tests on the NIPT cost in the UK page or our full fees list, and book online when you are ready.

Yes. TDL tests twin pregnancies with VeriSeq V2 from 10 weeks, whether conceived naturally or through IVF.

There are two things to be aware of. Fetal sex is reported as a single result covering both babies rather than one result each, so the test cannot tell you that one twin is a boy and the other a girl. And because two placentas contribute cell-free DNA, screening performance in twins is generally less well established than in singleton pregnancies.

A vanishing twin — where one twin has stopped developing — is a different situation, and not every NIPT platform is validated for it. Please tell us before booking; PrenatalSAFE is the option we would normally discuss in that circumstance. Illumina states the assay is not validated for pregnancies with more than two babies, so triplets and higher-order pregnancies are outside its scope.

Yes. TDL — The Doctors Laboratory — runs the assay at its genetics laboratory in London, on Illumina sequencing instruments.

For patients this mainly means speed and traceability. Your sample goes by courier across London rather than crossing a border, so there is no international shipping leg and no customs delay, and if a query arises the laboratory is in the same city and the same time zone as the clinicians looking after you.

TDL is one of the largest independent clinical laboratories in the UK and has provided prenatal screening to British clinics for many years, including the decade during which it ran the Harmony test.

From 10 weeks of pregnancy. The assay is validated in pregnancies of at least 10 weeks’ gestation, and TDL tests from that point.

We confirm your dates by ultrasound on the day rather than relying on your last menstrual period, because being even a few days early can mean the sample cannot be run. If you are unsure how far along you are, a viability scan at around 7-8 weeks will date the pregnancy so we can book your NIPT for exactly the right day.

Most people have the test alongside our 10 week scan. If you are already further on, NIPT can still be performed later in pregnancy, and an early fetal scan at 15-16 weeks or a nuchal scan at 11-14 weeks may be the more useful scan to pair it with. Testing in the first trimester is generally preferable, as it leaves the most time for any follow-up.

No. The package we offer covers trisomy 21, trisomy 18 and trisomy 13, with optional fetal sex determination. It does not include microdeletions, 22q11.2 deletion syndrome (DiGeorge syndrome) or single-gene disorders. 22q11.2 deletion is around 3 Mb, below the 7 Mb resolution Illumina states even for the assay’s genome-wide analysis, so it is not detectable by this test.

Sex chromosome conditions are a slightly different case. TDL offers an optional sex chromosome panel alongside this assay, but we do not include it as standard, because cell-free DNA screening for those conditions has more limited validation and a higher false-positive rate than trisomy screening. If you would like it, tell us before you book so we can talk it through first.

If you want broader coverage, Panorama adds sex chromosome aneuploidies, triploidy and 22q11.2 deletion, while the SMART Test is our most extensive package. There is no single right answer, and a broader panel is not automatically better — wider screening also generates more findings that need following up. NIPT genetic counselling is available if you would like a longer conversation, and you can compare every option on our best NIPT test in London page.

A ‘no call’ means the laboratory could not produce a reliable result from your sample, most often because the fetal fraction — the proportion of cell-free DNA coming from the placenta — was too low to analyse. In the manufacturer’s validation of the assay, 1.2 per cent of samples failed quality control at first pass, although that is a laboratory figure from a validation cohort rather than a service-level rate for TDL.

It is not a result in itself, and it is not an indication that anything is wrong. Fetal fraction rises as pregnancy progresses and tends to be lower at higher maternal body weight, so the usual next step is a second blood sample taken a week or two later, which resolves most cases.

We will call you to explain what happened, arrange the repeat sample and set out anything you need to know about timing or cost before you decide. If a second attempt is also unsuccessful, we would talk through the alternatives with you — a different NIPT platform, NHS combined screening, or a diagnostic test if your circumstances warrant it.

Please tell us before you book. Cell-free DNA testing analyses placental DNA, so a donor egg or surrogate pregnancy does not prevent screening in principle, but not every platform is validated for every situation and the laboratory needs to know in advance to interpret the result correctly.

PrenatalSAFE is the option we most often use for donor egg and surrogacy pregnancies, and it is the same £540 with our scan. If you would prefer the TDL laboratory, we will confirm suitability with TDL before your appointment rather than after your blood has been taken.

Fetal sex determination is unaffected by how the pregnancy was conceived. If you are also considering a wider panel, extended NIPT in London sets out which of our tests cover which situations.

Private NIPT is an addition to NHS antenatal care, not a replacement for it. We would always encourage you to keep your NHS appointments, your midwife’s continuity of care and your NHS anomaly scan at around 20 weeks, whichever private test you choose.

NHS combined screening at 11-14 weeks uses a nuchal translucency measurement together with blood markers and your age to estimate the chance of Down’s, Edwards’ and Patau’s syndromes. NIPT is more accurate for those three conditions, but the nuchal measurement itself carries information that a blood test does not — a raised nuchal translucency can point towards cardiac and other structural problems regardless of the chromosomes.

That is why we pair every NIPT with ultrasound, and why a nuchal scan at 11-14 weeks remains worth having in its own right. If a private result is high chance, we will help you bring it into your NHS pathway promptly so that any diagnostic testing and specialist care are arranged without delay.

Not through London Pregnancy Clinic — every NIPT we offer includes an expert ultrasound scan. The scan confirms your pregnancy is viable, dates it accurately and checks it is suitable for testing, which is why we do not offer the blood test on its own.

If you cannot get to our London clinic, our partner Jeen Health offers NIPT across the UK. You will need to provide proof of a pregnancy scan taken within the last 7 days before your blood sample is taken.