MSAFP is a single marker screening test performed on a maternal serum sample collected in the second trimester between 15 weeks / 0 days and 23 weeks / 6 days (15.0 - 23.9 weeks). The results provide a risk assessment for fetal open neural tube defects. It is appropriate to order this test following CVS or first trimester screening for fetal Down syndrome, as these analyses do not screen for open neural tube defects.
Risk assessment for fetal open neural tube defects.
AFP, Maternal Serum; Alpha-Fetoprotein (AFP), Maternal Serum for Open Spina Bifida; Maternal Serum α-Fetoprotein; msAFP;
Immunochemiluminometric assay (ICMA)
Whole blood or serum (unhemolyzed)
Serum: 2-3 mL
Whole Blood: 7 mL
Serum: AFP tube
Whole Blood: Serum separator tube (SST) or red-top tube
Whole Blood: allow to clot; centrifuge (15 minutes at 1,500 rpm) to prevent hemolysis.
Causes for Rejection
Gross hemolysis; gross lipemia; quantity not sufficient for analysis