Can trisomy 21 NIPT test be wrong?

Your patient’s NIPT result suggests the presence of an extra copy of chromosome 21. NIPT is a screening test; false positives can occur. The actual chance for the pregnancy to have trisomy 21 depends on many factors, including the patient’s clinical and family history.

How accurate is NIPT for trisomy 21?

What is the general accuracy of NIPT? The screening has a detection rate of above 99 percent for the three most common chromosome abnormalities, trisomy 21, trisomy 18, and trisomy 13. The false-positive rate is well under 1 percent.

Can Down syndrome test be wrong NIPT?

The most likely reason for this result is that the baby has Down syndrome. However, there is a small chance for a “false positive” result. A false positive result is when the test shows a high risk for Down syndrome, but the baby does not have this condition.

Can you get a false-positive for trisomy 21?

High risk for trisomy 21

A false positive result means that although NIPT indicates a high risk of trisomy 21, the baby does not have this condition. The only way to provide a definitive diagnosis is to have a diagnostic procedure (CVS or amniocentesis) with chromosome testing.

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How accurate is genetic testing for trisomy 21?

The clinical specificity for any trisomy was 99.9% (95% CI 99.8%–99.9%). Compared with traditional prenatal screening, NIPT was more accurate in detecting trisomies 21, 18, and 13, and decreased the need for diagnostic testing.

How often is the NIPT wrong?

What are the odds it could be wrong? The chances of a sex determination via NIPT being wrong is around 1 percent when the test is conducted after week 10 of your pregnancy or later, Schaffir says.

Can amniocentesis be wrong?

What the results mean. Amniocentesis is estimated to give a definitive result in 98 to 99 out of every 100 women having the test. But it cannot test for every condition and, in a small number of cases, it’s not possible to get a conclusive result. Many women who have amniocentesis will have a “normal” result.

Why can NIPT be wrong?

The common causes of false positive NIPT results include placental mosaicism [8], foetal chromosome rearrangement, vanishing twin or co-twin demise [11], and familial chromosome abnormalities or malignancy [12].

What causes false positive NIPT?

CPM is the most common cause of false-positive NIPT results and occurs more frequently for trisomy 13 and monosomy X than it does for either trisomy 18 or trisomy 21 (3). To help address this problem, VCGS calculates a mosaicism score on every trisomic sample called.

Can NIPT test be wrong for Edwards?

Conclusions: NIPT using cell-free fetal DNA has very high sensitivity and specificity for Down syndrome, with slightly lower sensitivity for Edwards and Patau syndrome. However, it is not 100% accurate and should not be used as a final diagnosis for positive cases.

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What if my NIPT test is positive?

If you have a positive NIPT result, your healthcare provider will likely order additional diagnostic tests. In some cases, these diagnostic tests reveal that the baby doesn’t have a chromosomal abnormality after all.

What percentage of NIPT tests come back high risk?

The likelihood that a 25 year old who receives a high risk NIPT for trisomy 21 will truly have a baby with trisomy 21 is approximately 33%. The likelihood that a 40 year old who receives a high risk NIPT for trisomy 21 will truly have a baby with trisomy 21 is approximately 87%1.