Unexplained False Negative Results in Noninvasive Prenatal Testing: Two Cases Involving Trisomies 13 and 18

Table 1

Survey of published cases of false negative NIPT by massive parallel shotgun sequencing with (molecular) cytogenetic follow-up included¹.

Trisomy	Study [reference]	Indication for NIPT	Case,; mat. age	Blood drawn at GA^2	Fetal DNA fraction (effective fetal DNA fraction)	Result of NIPT	Karyotype	Explanation for false negative NIPT result
13	Canick et al. (2013) [17]	Ultrasound abnormalities	Case  1; 34 yrs	14 w	6% (0.6%)	-score 0.08 for chromosome 13	46,XX/47,XX,+13 in cultured amniocytes	Amniocentesis showed 10% mosaicism for a cell line with +13
18	Canick et al. (2013) [17]	Maternal age	Case  5; 39 yrs	12 w	23% (10%)	-score 0.22 for chromosome 18	47,XY,+21/48,XY,+18,+21 in CVS	CVS showed 45% mosaicism for a cell line with both +18 and +21
18	Gao et al. (2014) [25]	1/70 risk for tri-21 by combined 1st trim. test	43 yrs	13 w	7.4%	Low risk tri-13,; tri-18, and tri-21, high risk XXX	48,XXX,+18 in cultured amniocytes	Estimated 20–30% of placental cells studied by FISH were +18, with QF-PCR showing variable levels of +18 cells across the placenta
18	Mao et al. (2014) [26]	1/313 risk for tri-18 by serum screening	22 yrs	17 w	11.6% (4.1%)	-score 0.35 for tri-18; -score 4.4 for tri-21	47,XX,+18 in cultured amniocytes	Placental biopsies showed on average 50% +21, 35% +18, and 15% normal cells, but at least one region had 61% +21 but only 22% +18
18	Pan et al. (2014) [27]	1/45 risk for tri-21 by combined test	24 yrs	18 w	Not provided	-score −0.52 for tri-18; -score −4.05 for X-chromosome	47,XX,+18 in cultured amniocytes, both by karyotyping and SNP-array	About 30% of placental cells studied by FISH were +18, and about 67% were 45, X; SNP-array was indicative of ~50% cells with +18
18	Zhang et al. (2015) [28]	1/360 risk for tri-21 by combined test	29 yrs	19 w	5.3% (1.1–2.2%)	Aneuploidy not detected	47,XY,+18 in products of conception	6 placental biopsies showed 20–40% cells with +18
18	Zhang et al. (2015) [28]	1/45 risk for tri-21 by combined test	24 yrs	20 w	9.5% (2.9%)	Indicative of 45,X	47,XX,+18 in cultured amniocytes	In placental tissue 30% of the cells showed +18 and 60% showed 45,X
21	Canick et al. (2013) [17]	Maternal age	Case  2; 44 yrs	11 w	17% (1.7%)	-score 2.03 for chromosome 21	46,XY20/47,XY,+212 in CVS	CVS showed 9% mosaicism for a cell line with +21
21	Canick et al. (2013) [17]	Maternal age	Case  3; 41 yrs	12 w	9% (4.5%)	-score −1.25 for chromosome 21	46,XY/47,XY,+21 in CVS	50% mosaicism by CVS; possibly this was lower in the placenta as a whole
21	Wang et al. (2013) [29]	1/370 risk for tri-21 by serum screening at 17 w	Case  1; 32 yrs	18 w	15.6%	-score 2.04^3 for chromosome 21	46,XX,der(21;21)(q10;q10),+21 in fetal blood (cordocentesis)	Placental biopsies had 17%, 21%, 23%, and 53% cells with +21
21	Wang et al. (2013) [29]	2 spontaneous abortions	Case  2; 35 yrs	18 w	19.7%	-score 1.33 for chromosome 21	47,XY,+21 in cultured amniocytes	Placental biopsies had 2%, 51%, and 76% cells with +21
21	Smith et al. (2014) [30]	CAVCD^4	32 yrs	20 w	Not provided	“Negative” for trisomy 21	47,XX,+21 in postnatal blood	No study of placenta or umbilical cord; no explanation provided

Notes. ¹A false negative case of trisomy 21 was also mentioned by Wang et al. [31], 2 other false negative trisomy 21 cases were mentioned by Dar et al. [32], and another 6 false negative trisomy 21 cases were described by Zhang et al. [28]; a false negative case of trisomy 18 was mentioned by Beamon et al. [33], another one by Quezada et al. [34] and by Zhang et al. [28]; 3 false negative cases of tri-13 were reported by Quezada et al. [34]; all of these were without further investigation of the possible causes of the discrepant findings.
²GA: gestational age.
³In a repeat blood sample taken at 24 weeks the -score for chromosome 21 was 4.0 and trisomy-21 was reported as a result.
⁴CAVCD: complete atrioventricular canal defect.