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HelpTest Code MAFP1 Alpha-Fetoprotein (AFP), Single Marker Screen, Maternal, Serum
Necessary Information
In order to provide the best results, either answer the order entry questions or provide the required information using the Second Trimester Maternal Screening Alpha-Fetoprotein / Quad Screen Patient Information (T595).
Specimen Required
Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Do not collect specimen after amniocentesis as this could affect results.
2. Centrifuge and aliquot serum into plastic vial within 2 hours of collection.
Additional Information:
1. Collect blood between 15 weeks, 0 days and 22 weeks, 6 days.
2. Initial or repeat testing is determined in the laboratory at the time of report and will be reported accordingly. To be considered a repeat test for the patient, the testing must be within the same pregnancy and trimester, with interpretable results for the same test, and both tests are performed at Mayo Clinic.
Forms
1. Second Trimester Maternal Screening Alpha-Fetoprotein / Quad Screen Patient Information (T595) is required
2. If not ordering electronically, complete, print, and send a General Request (T239)
Useful For
Prenatal screening for open neural tube defect
Special Instructions
Method Name
Two-Site Immunoenzymatic (Sandwich) Assay
Reporting Name
AFP Single Marker SCRN, Maternal, SSpecimen Type
SerumSpecimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 14 days | |
| Frozen | 90 days | ||
| Ambient | 7 days |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | OK |
| Gross icterus | OK |
Clinical Information
Alpha-fetoprotein (AFP) is a fetal protein that is initially produced in the fetal yolk sac and liver. A small amount is produced by the gastrointestinal tract. By the end of the first trimester, nearly all AFP is produced by the fetal liver. The concentration of AFP peaks in fetal serum between 10 to 13 weeks. Fetal AFP diffuses across the placental barrier into the maternal circulation. A small amount also is transported from the amniotic cavity.
The AFP concentration in maternal serum rises throughout pregnancy, from the nonpregnancy level of 0.2 ng/mL to about 250 ng/mL at 32 weeks gestation. If the fetus has an open neural tube defect (NTD), AFP is thought to leak directly into the amniotic fluid causing unexpectedly high concentrations of AFP. Subsequently, the AFP reaches the maternal circulation, producing elevated serum levels. Other fetal abnormalities such as omphalocele, gastroschisis, congenital kidney disease, esophageal atresia, and other fetal distress situations (eg, threatened abortion and fetal demise) also may result in maternal serum AFP elevations. Increased maternal serum AFP concentrations also may be seen in multiple pregnancies and in unaffected singleton pregnancies in which the gestational age has been underestimated.
Lower maternal serum AFP concentrations have been associated with an increased risk for genetic conditions such as trisomy 21 (Down syndrome) and trisomy 18 (Edwards syndrome). Risks for these syndrome disorders are only provided with the use of multiple marker screening (QUAD1 / Quad Screen [Second Trimester] Maternal, Serum).
Measurement of maternal serum AFP values is a standard tool used in obstetrical care to identify pregnancies that may have an increased risk for NTD. The screen is performed by measuring AFP in maternal serum and comparing this value to the median AFP value in an unaffected population to obtain a multiple of the median (MoM). The laboratory has established a MoM cutoff of 2.5, which classifies each screen as either screen-positive or screen-negative. A screen-positive result indicates that the value obtained exceeds the established cutoff. A positive screen does not provide a diagnosis but indicates that further evaluation should be considered.
Reference Values
NEURAL TUBE DEFECTS:
An alpha-fetoprotein (AFP) multiple of the median (MoM) <2.5 is reported as screen negative.
AFP MoM ≥2.5 (singleton and twin pregnancies) are reported as screen positive.
An interpretive report will be provided.
Interpretation
Neural tube defects:
A screen-negative result indicates that the calculated alpha-fetoprotein (AFP) multiple of the median (MoM) falls below the established cutoff of 2.50 MoM. A negative screen does not guarantee the absence of neural tube defects (NTD).
A screen-positive result indicates that the calculated AFP MoM is 2.50 or greater and may indicate an increased risk for open NTD. The actual risk depends on the level of AFP and the individual's pretest risk of having a child with NTD based on family history, geographical location, maternal conditions such as diabetes and epilepsy, and use of folate prior to conception. A screen-positive result does not infer a definitive diagnosis of a NTD but indicates that further evaluation should be considered. Approximately 80% of pregnancies affected with an open NTD have elevated AFP MoM values greater than 2.50.
Follow up:
Upon receiving maternal serum screening results, all information used in the risk calculation should be reviewed for accuracy (ie, weight, diabetic status, gestational dating). If any information is incorrect the laboratory should be contacted for a recalculation of the estimated risks.
Screen-negative results typically do not warrant further evaluation.
Ultrasound is recommended to confirm dates for NTD screen-positive results. If ultrasound yields new dates that differ by at least 7 days, a recalculation should be considered. If dates are confirmed, high-resolution ultrasound and amniocentesis (including amniotic fluid AFP and acetylcholinesterase measurements for NTD) are typically offered.
Day(s) Performed
Monday through Friday
Report Available
4 to 6 daysSpecimen Retention Time
14 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
82105
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| MAFP1 | AFP Single Marker SCRN, Maternal, S | 48802-3 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 7058 | Recalculated Maternal Serum Screen | 32399-8 |
| 113146 | Results Summary | 32399-8 |
| 113147 | Neural tube defect risk estimate | 48803-1 |
| 10351 | AFP | 83073-7 |
| 113148 | AFP MoM | 23811-3 |
| 10356 | INTERPRETATION | 49092-0 |
| 10357 | RECOMMENDED FOLLOW UP | 80615-8 |
| 10248 | Additional comments | 48767-8 |
| 3009 | Specimen collection date | 33882-2 |
| 7823 | Maternal date of birth | 21112-8 |
| 7834 | Calculated age at EDD | 43993-5 |
| 26717 | Maternal Weight | 29463-7 |
| 26718 | Maternal Weight | 29463-7 |
| IDD | Insulin dependent diabetes | 44877-9 |
| RACE1 | Patient race | 21484-1 |
| SMKNG | Current cigarette smoking status | 64234-8 |
| 10054 | EDD by U/S scan | 11781-2 |
| 7203 | GA on collection by U/S scan | 11888-5 |
| 7753 | EDD by LMP | 11779-6 |
| 7204 | GA on collection by dates | 11885-1 |
| 7830 | GA used in risk estimate | 21299-3 |
| MULTF | Number of Fetuses | 55281-0 |
| CHOR_ | Number of Chorions | 92568-5 |
| IVFP | IVF pregnancy | 47224-1 |
| PRNTD | Prev Pregnancy w/ Neural Tube Defect | 53827-2 |
| PTNTD | Patient or father of baby has a NTD | 53827-2 |
| INTL | Initial or repeat testing | 77202-0 |
| DRPHN | Physician Phone Number | 68340-9 |
| 10358 | GENERAL TEST INFORMATION | 62364-5 |