Stepwise, Part 2
Use
Prenatal screening that completes the Stepwise, Part 2 screen when a first-trimester Part 1 test has already been performed. It measures multiple serum markers—AFP, unconjugated estriol, hCG, inhibin A (dimeric), PAPP‑A, and hCG from Part 1—to refine the risk assessment for fetal trisomy 21 (Down syndrome), trisomy 18, and open neural tube defects in the second trimester of pregnancy.
Special Instructions
Collect between 14.0 weeks to 22 6/7 weeks of gestation. Complete all required maternal demographic and clinical information (mother’s date of birth, estimated date of delivery by US/LMP/PE, maternal weight, race, insulin‑dependent diabetes status, repeat sample (Y/N), number of fetuses, and neural tube defect history) for accurate interpretation. Use transport tube, room temperature transport. This test cannot be used for New York patients (use test code 16466 instead) and is not available in California.
Limitations
A negative screen does not guarantee a healthy fetus; it only assesses risk for trisomy 21, trisomy 18, and ONTDs. Accuracy depends on accuracy of demographic data and gestational dating. Positive results warrant follow‑up diagnostic testing. Samples collected outside the 14.0–22 6/7 week window may be invalid. Demographic inaccuracies can lead to miscalculated risk.
Methodology
Immunoassay (Multiplex Protein Panel)
Biomarkers
Result Turnaround Time
Not provided.
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
3 mL
Minimum Volume
1 mL
Container
Transport tube
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 14 days |