Screening tests for trisomy 21 (Down syndrome)

Blood at 11+0 to 13+6  

NT at 10+3 to 13+6

• Results can be available in the first trimester
• Also detects trisomy 18 and often trisomy 13
• Does not screen for neural tube defects

Blood at 15+0 to 18+6 (can be through 22+6)

• Does not require ultrasound
• Can be offered to patients presenting for prenatal care in the second trimester
• Also detects trisomy 18 and neural tube defects

PAPP-A+NT

and

hCG, AFP, uE3, DIA

First blood draw and NT are at the same time as for combined test  

Second blood draw is at the same time as for quadruple test

94% / 5%

or

85% / 2%

• Highest detection rate for serum/ultrasound tests.
• Also detects trisomy 18 and often trisomy 13.
• In the sequential format, the first-trimester results are reported if very high (eg, ≥1 in 50); remaining patients go on to complete the second trimester part of the test.

Same as integrated but without NT

First blood draw at the same time as for combined test

Second blood draw is at the same time as for quadruple test

• Highest sensitivity and specificity for all trisomies
• Also detects sex chromosome aneuploidies
• 1-3% of tests fail (no result)
• Reasonable to use for secondary screening after a prior serum screen positive before moving on to diagnostic testing