NHS  Some multi-marker screening is now available.  Our Genmark™, Addmark®  and Nuchal+ use additional markers to increase risk accuracy.

Down's syndrome  The most common cause of severe learning disability.  There are associated medical problems: but many are healthy and have a good life span.

Edwards' syndrome  Ten-times less common than Down's syndrome; nearly all affected die in early infancy.

Spina bifida  Failure of the neural tube to close causes physical disability but generally no mental handicap.

Ultrasound alone  The main marker is nuchal translucency at 11-13 weeks or nuchal skinfold at 14-20 weeks.  Many centres also determine nasal bone.

Genmark™ : (£195)  Combines four blood markers and two ultrasound markers at 14-20 weeks.

Addmark® : (£195)  Combines four blood markers and two ultrasound markers at 9-13 weeks.  If risk is borderline, four more blood markers tested after 14 weeks gestation and risk revised.

Nuchal+: (£100)  Nuchal translucency at 11-13 weeks plus nasal bone determination.

Using our additional markers, more pregnancies with Down's syndrome are shown to have a high risk (i.e. 'detected') and overall fewer pregnancies are given a risk which is high (i.e. 'positive').

Test*	Week	Detected**	Positive
Genmark™	14-18	80%	2.7%
Addmark®	9-13	93%	0.6%
Nuchal+	11-13	89%	2.8%

*Occasionally nasal bone not seen and rate lower
**Also, Edwards' syndrome about 90% if 9-13 weeks; spina bifida about 75% if 15-20 weeks.

The above table gives overall rates for UK women.  Because the risk of Down's syndrome increases with maternal age, the percentage of Down's syndrome pregnancies with high risk and the percentage of pregnancies with high risk also increases. 

	Age 25			Age 30			Age 35			Age 40
Test	Detected	Positive		Detected	Positive		Detected	Positive		Detected	Positive
Genmark™	87%	0.8%		89%	1.1%		92%	2.2%		95%	5.9%
Addmark®	92%	0.4%		92%	0.6%		93%	1.1%		94%	2.0%
Nuchal+	83%	1.2%		87%	2.2%		88%	2.9%		92%	7.6%

The above tables give the test accuracy for women who do not have twins. The accuracy in twins depends on whether they are identical or not which can be determined by examination of the sacs and membranes. In identical twins the accuracy of Tipmark, Genmark™ and Addmark® is similar to that in non-twins, but when the twins are not identical accuracy is lower.

Test	Detected	Positive
Genmark™	66%	2.8%
Addmark®	89%	1.9%

The results are available immediately after the scan. However, if the blood sample is taken at the time of the ultrasound scan then a result is usually available in 3 – 5 working days. If the results are not given at the time of the scan then all women will be informed of the result of their screening test by telephone and in writing. The actual risk of Down's syndrome will be expressed numerically (as a risk of 1 in …) in addition to the conclusion, screen positive or screen negative.

Biochemical markers are not always present in affected pregnancies and conversely, ultrasound markers are not always present. By using a combination of biochemistry and ultrasound scan, the chance of detecting a marker or combination is increased and, thus, the detection and false positive rates are improved across all the age groups.

With advances in medical research a blood test and/or ultrasound scan in early pregnancy can be used to screen more effectively and identify high risk individuals.

For further information please download the Genome brochure.