Alpha-Fetoprotein (AFP), Single Marker Screen, Maternal, Serum
Use
Alpha-fetoprotein (AFP) testing is a key component in prenatal screening for open neural tube defects (NTDs). By measuring the AFP levels in maternal serum and comparing them to the median level in an unaffected population, clinicians can estimate the risk for NTDs. Elevated AFP levels can indicate a potential increase in risk for these and other fetal conditions, suggesting the need for further evaluation. However, a screen-positive result does not confirm a diagnosis, as it merely signifies that the AFP levels exceed the established cutoff, prompting detailed follow-up assessments such as high-resolution ultrasounds and amniocentesis.
Special Instructions
It's critical to provide accurate gestational age, weight, and personal medical history for precise risk assessment. A Second Trimester Maternal Screening Alpha-Fetoprotein / Quad Screen Patient Information form (T595) should be submitted, especially if not ordering electronically. Blood should be collected between 15 to 22 weeks of pregnancy, ensuring samples are handled and transported according to guidelines to maintain integrity.
Limitations
Multiple factors such as race, weight, insulin-dependent diabetes, and smoking status can affect the AFP concentration and modify the risk calculations. Accurate gestational dating, preferably via ultrasound, is essential to avoid false-positive or negative results. Furthermore, valid AFP measurements cannot be taken after amniocentesis. Triplet or higher multiple pregnancies are not feasible for this screening, as the interpretations cannot accommodate such complexities. Possible interference in immunoassays due to human anti-mouse antibodies should be considered if results do not match clinical expectations.
FDA ApprovedNew York Approved
Methodology
Immunoassay (CLIA)
Biomarkers
LOINC Codes
- 48802-3
- 44877-9
- 47224-1
- 55281-0
- 49092-0
- 48767-8
- 80615-8
- 62364-5
- 32399-8
- 33882-2
- 21112-8
- 43993-5
- 29463-7
- 11781-2
- 11779-6
- 11888-5
- 11885-1
- 21299-3
- 83073-7
- 48803-1
- 23811-3
- 21484-1
- 64234-8
- 92568-5
- 53827-2
- 77202-0
- 68340-9
Result Turnaround Time
4-6 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.5 mL
Container
Plastic vial
Collection Instructions
Do not collect specimen after amniocentesis as this could affect results. Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.
Causes for Rejection
Gross hemolysis
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days |
| Refrigerated | 14 days |
| Frozen | 90 days |