Clinical utility of noninvasive fetal trisomy (NIFTY) test – early experience

Figures & data

Table I.  Basic patient characteristics.

Characteristics	Number of cases (%), N = 567
Maternal age
20–24	4 (0.71%)
25–29	38 (6.70%)
30–34	144 (25.40%)
35–39	252 (44.44%)
40–44	127 (22.4%)
≥45	2 (0.35%)
Gestation at NIFTY test
12W–13W6D	279 (49.21%)
14W–15W6D	122 (21.52%)
16W–20W6D	142 (25.04%)
21 week and above	24 (4.23%)
Previous trisomy 21 pregnancies	6 (1.06%)
Family history of trisomy 21	10 (1.76%)
Ethnicity
Chinese	524 (92.42%)
Caucasian	29 (5.11%)
Others	14 (2.47%)
Prior Down syndrome screening test
None	194 (34.22%)
Combined first-trimester NT + biochemistry	288 (50.79%)
First-trimester NT (± other Ultrasound (USG) markers) only	24 (4.23%)
First-trimester biochemistry only	10 (1.76%)
Second-trimester biochemistry only	41 (7.23%)
Other tests, or more than one test	10 (1.76%)
Result of prior screening tests (n = 373)
High risk	179 (47.99%)
Low risk	124 (33.24%)
Result not available at time of NIFTY test	70 (18.77%)

NIFTY, noninvasive fetal trisomy; NT, nuchal translucency.

Table II.  Characteristics of the nine NIFTY-positive cases.

	Age	Prior screening	NIFTY result	Karyotyping	Outcome
Case 1	40	Dual test (1:19)	High risk T21	T21	TOP
Case 2	35	NT 3.9 mm	High risk T21	T21	TOP
Case 3	36	No	High risk T21	T21	TOP
Case 4	28	FTCS (1:40)	High risk T21	T21	TOP
Case 5	38	FTCS (1:5)	High risk T21	T21	TOP
Case 6	33	NT 4.1 mm	High risk T21	T21	TOP
Case 7	37	FTCS 1:4	High risk T18	T18	TOP
Case 8	36	No	High risk T21	T21	TOP
Case 9	38	NT 3.4 mm	High risk T21	T21	TOP

FTCS, first-trimester-combined screening; NIFTY, noninvasive fetal trisomy; NT, nuchal translucency; TOP, termination of pregnancy; T18, trisomy 18; T21, trisomy 21.

Table III.  Result of patient satisfaction survey.

Survey question	Number (%), N = 182
Prior screening test
No	48 (26.3%)
One screening test	125 (68.7%)
>1 screening test	9 (5.0%)
Primary reason for requesting NIFTY test
Told to be high or borderline risk, to avoid invasive test	70 (38.46%)
Told to be low risk, still worry	51 (28.02%)
>1 screening tests with conflicting result	5 (2.75%)
As primary screening test because it is the best	40 (21.98%)
Just told by her doctor to have the test	16 (8.79%)
How much the NIFTY result helped to reduce her anxiety
Completely relaxed	95 (52.20%)
Almost completely relaxed. Minimal anxiety which is  difficult to quantify.	80 (43.96%)
Helped a lot, but still worry about Down syndrome about  once a week	4 (2.20%)
Still constantly worrying about Down syndrome almost  everyday	3 (1.65%)
Did not help at all	0 (0%)
Will she recommend NIFTY test to her friends
Yes, as a primary screening test	117 (64.29%)
Yes, as a secondary screening test	65 (35.71%)
No	0 (0%)
Strength of recommendation
Very strong	53 (29.12%)
Strong	122 (67.03%)
Weak	7 (3.85%)
Very weak	0 (0%)
Reporting time
Far too long to be acceptable	4 (2.20%)
Too long, but still acceptable	14 (7.69%)
Pretty acceptable. But shorter would be better	107 (58.79%)
I am OK with the reporting time	57 (31.32%)
Overall satisfaction
Very satisfied	74 (40.66%)
Satisfied	107 (58.79%)
Neither	1 (0.55%)
Dissatisfied	0 (0%)
Very dissatisfied	0 (0%)

NIFTY, noninvasive fetal trisomy.

Table IV.  The chance of an affected fetus given a positive noninvasive fetal trisomy test result, the positive predictive value, is affected by the prevalence of the condition in the test population and the false-positive rate. Whether the detection rate is 99% or 100%, it does not have a significant effect.

PPV
FPR	Prevalence of 0.2%	Prevalence of 0.5%
1.00%	16.7%	33.4%
0.50%	28.6%	50.1%
0.25%	44.5%	66.8%
0.10%	66.7%	83.4%

FPR, false-positive rate; PPV, positive predictive value.