Unexplained False Negative Results in Noninvasive Prenatal Testing: Two Cases Involving Trisomies 13 and 18
Table 2
Demographics and summary of laboratory testing in two cases with false negative NIPT.
Case; age (status)
BMI
Medication, alcohol, and drugs
1st trimester combined screening (NT)
Blood for NIPT drawn at GA1
Result of NIPT issued by a third party
Pregnancy outcome; cytogenetic follow-up
Fetal fraction
Tri-13
Tri-18
Tri-21
Case 1 35 yrs (G1P0)
22.0
Negative
1 : 190 risk for trisomy-18 (NT 1.6 mm)
13 5/7
8.8%
<1/10,000
<1/10,000
<1/10,000
Amniocentesis at 21 weeks showed a nonmosaic 47, XY, +13 karyotype; sampling of placenta (9 biopsies) gave no evidence for the presence of euploid cells
Case 2 40 yrs (G2P1)
22.4
Negative
Not performed
11 0/7
10.7%
<1/10,000
<1/10,000
<1/10,000
Amniocentesis at 20 weeks showed a nonmosaic 47, XX, +18 karyotype; sampling of placenta (10 biopsies) showed that a maximum of 20–30% euploid cells may have been present in the cytotrophoblast
