A new review looked at 20 studies with over 67,500 people to see how well a blood test called cell-free DNA non-invasive prenatal testing (NIPT) works. This test checks a pregnant person's blood for small pieces of the baby's DNA to screen for certain chromosome problems.
The review found that NIPT is extremely good at detecting Trisomy 21, also known as Down syndrome. It correctly identified all cases (100% sensitivity) and correctly ruled out the condition in all healthy pregnancies (100% specificity). For Trisomy 18 and Trisomy 13, the test was also very accurate, though slightly less so, with sensitivity ranging from about 92% to 100% for Trisomy 18 and 79% to 100% for Trisomy 13.
However, the test was less consistent for other chromosome issues. For sex chromosome aneuploidies (like Turner syndrome), sensitivity ranged from 75% to 100%. For copy number variations (small missing or extra pieces of chromosomes), sensitivity was even lower, from about 54% to 98%. This means the test may miss some of these conditions.
The review also noted that NIPT can sometimes give results that don't match the actual condition (discordant outcomes), especially for sex chromosome aneuploidies and microdeletions. This is important for patients to understand.
Overall, NIPT is a highly effective screening tool for the most common trisomies, but it is not perfect for all chromosome problems. If a NIPT result is positive, a diagnostic test like amniocentesis is still needed to confirm.
