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The basic NIPT test looks for chromosome 21 trisomy, chromosome 18 trisomy, chromosome 13 trisomy and sex chromosomes, while the all-chromosome aneuploidy test looks for abnormal numbers of chromosomes 1 to 22 and all sex chromosomes (aneuploidy).
From the table below, it can be said that the chorionic villus biopsy is positive at a rate of 0.56%, or about 1 in 200, while the amniotic fluid test is positive at a rate of 0.05%, or about 1 in 2000.
Positivity rates for total chromosome aneuploidy in chorionic biopsy and amniotic fluid testing
| 21, 18 and 13 trisomy | Other trisomy | |
|---|---|---|
| Number of samples in chorionic biopsy |
5.06% (532 out of 10,511) |
0.56% (59 out of 10,511) |
| Number of samples in amniotic fluid testing |
1.02% (748 out of 73,268) |
0.05% (30 out of 73,268) |
| Number of samples from both chorionic biopsy and amniocentesis tests |
2.1% (235 out of 11,066) |
0.12% (13 out of 11,066) |
1. Konialis C, Pangalos C. Dilemmas in prenatal chromosomal diagnosis revealed through a single center’s 30 years’ experience and 90,000 cases. Fetal Diagn Ther 2015; 38(3):218-232.
2. Comas C, Echevarria M, Rodríguez I, Serra B, Cirigliano V. Prenatal invasive testing: a 13-year single institution experience. J Matern Fetal Neonatal Med 2014 Aug;27(12):1209-12.
Reported positive by trisomy type for all chromosome aneuploidy test
（excluding mosaicism）
| Trisomy １ | Exhausted egg |
|---|---|
| Trisomy ２ | Incapable of survival |
| Trisomy ３ | No positive reports |
| Trisomy ４ | Rarely：Incapable of survival |
| Trisomy ５ | Incapable of survival |
| Trisomy ６ | Incapable of survival |
| Trisomy ７ | Incapable of survival |
| Trisomy ８ | Incapable of survival |
| Trisomy ９ | There are surviving cases |
| Trisomy 10 | Incapable of survival |
| Trisomy 11 | Incapable of survival |
| Trisomy 12 | Incapable of survival |
|---|---|
| Trisomy 13 | There are surviving cases |
| Trisomy 14 | Incapable of survival |
| Trisomy 15 | There are surviving cases |
| Trisomy 16 | Incapable of survival |
| Trisomy 17 | Incapable of survival |
| Trisomy 18 | Incapable of survival |
| Trisomy 19 | Extremely rare：Incapable of survival |
| Trisomy 20 | There are surviving cases |
| Trisomy 21 | There are surviving cases |
| Trisomy 22 | There are surviving cases |
FAQs about whole chromosome testing
Q: Does an whole chromosome test reveal all chromosomal abnormalities in the foetus?
To test for structural abnormalities such as chromosome deletions and duplications as well as abnormal numbers of chromosomes, an all-autosomal whole-region partial deletion/duplication disease test※ is required.
For more information on total autosomal partial deletion/duplication diseases, see ‘What is total autosomal partial deletion/duplication disease’.
※Limited, however, to anomalies of 7 million bases or more
