Alternative names, keywords |
Downs, trisomy 21, trisomy 18, trisomy 13, first trimester screening, combined screening. |
Samples required |
Blood samples are taken as necessary via antenatal departments following ultrasound imaging, and must be accompanied by the correct request form. Full completion of this request form is essential for risk calculation. |
Test indications |
Combined screening for Down (trisomy 21), Edwards (trisomy 18) and Patau (trisomy 13) syndromes is done as part of the UHSussex Fetal Anomaly Screening Programme (FASP). The combined screening can only be completed when the crown rump length (CRL) of the fetus is between 45.0 and 84.0 mm (approximate gestation age of 11+2 to 14+1). However, the blood sample can be taken between 10+0 and 14+1 (as determined by the CRL). If this window is missed, samples can be referred for second trimester screening (see below). |
Reference range |
See report. |
Turnaround time |
3 working days |
Enquiries |
Biochemistry (Special Chemistry) |
Second trimester Down's screen

Alternative names, keywords |
Quadruple test, quad test. |
Samples required |
Blood samples are taken as necessary via antenatal departments following ultrasound imaging between 14 weeks +2 days and 20 weeks +0 days of gestation. Samples must be accompanied by the correct request form. Full completion of this request form is essential for risk calculation. |
Test indications |
Down's screening in second trimester. |
Reference range |
See report. |
Turnaround time |
3 working days from receipt in referral lab. |
Enquiries |
Biochemistry (Special Chemistry) |