Alpha-Fetoprotein, Amniotic Fluid
Use
Alpha-fetoprotein (AFP) is a glycoprotein synthesized mainly in the liver and yolk sac of the fetus. Measuring AFP in amniotic fluid is utilized for screening open neural tube defects and other fetal abnormalities such as omphalocele, gastroschisis, congenital kidney disease, and esophageal atresia. It also assists in follow-up testing for patients with elevated serum AFP levels or in conjunction with cytogenetic testing as elevated AFP may indicate fetal distress scenarios. The test helps in the detection of fetal abnormalities through diffusion of AFP into the amniotic fluid across the placenta.
Special Instructions
This test should be performed with caution as it is for screening purposes only. Incorrect gestational dating and benign factors may cause elevated AFP levels. The presence of human anti-mouse antibodies (HAMA) or heterophile antibodies may cause interference in immunoassays. Acetylcholinesterase analysis is recommended as an essential confirmatory test for specimens with positive AFP results.
Limitations
The AFP test is not specific for neural tube defects and should be used in combination with other procedures like ultrasonography and acetylcholinesterase measurements. False positives may occur due to a bloody tap causing elevated AFP and AChE levels, and negative results do not guarantee the absence of defects. Care must be taken in interpreting results, particularly if they do not align with clinical presentations.
FDA ApprovedNew York Approved
Methodology
Immunoassay (Other)
Biomarkers
LOINC Codes
- 58735-2
- 1832-5
Result Turnaround Time
2-19 days
Related Documents
For more information, please review the documents below
Specimen
Amniotic Fluid
Volume
0.75 mL
Minimum Volume
0.5 mL
Container
Plain, plastic, screw-top tube
Collection Instructions
Do not centrifuge.
Patient Preparation
Gestational age must be between 13 and 24 weeks; 16 to 18 weeks preferred.
Causes for Rejection
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days |
| Refrigerated | 7 days |