Sequential 2

Alphabetical Test listing

Sequential 2-13501

Sequential 2
AFP, maternal
Down syndrome
  • Screening test for open neural tube defects, Down syndrome, and trisomy 18.


5.0 mL
3 mL

Patient must have submitted a previous specimen in the first trimester for the Sequential 1 test. Gestational age will be based on crown rump length provided with the first trimester specimen.

  • Collect between 15.0 and 21.9 weeks of gestation

  • Maternal serum specimens must be drawn prior to amniocentesis to avoid contamination with fetal blood. laboratory.
  1. Allow blood to clot
  2. Separate serum from cells by centrifugation - pour off is not advised.



Gold serum separator (SST) tube



Ambient (preferred) - 7 days

Refrigerated - 14 days

Frozen - 14 days

  • Gross hemolysis
  • Gross lipemia
  • Quantity not sufficient for analysis (QNS)
  • Improper specimen type
LabCorp RTP (017750): R-LC
Mo - Sa
2 - 5 days

Chemiluminescent immunoassay (CLIA)


An interpretive report will be provided


Sequential screening provides a first trimester risk assessment.

Following the Sequential 1 blood draw, the PAPPA-A, hCG, NT, and other provided demographics are used to give a risk for Down syndrome and trisomy 18. If the risk is greater than 1 in 45 for Down syndrome or 1 in 100 for T18, then it is considered screen positive and it is recommended to offer diagnostic testing. If the risks are less than those cut offs then it is recommended to draw for the Sequential 2.

After the 2nd draw, a new risk is calculated for Down syndrome, trisomy 18 and open spina bifida using data from the first and second draws.

Result 1834-1