Test Catalog

Test Id : MAFP1

Alpha-Fetoprotein (AFP), Single Marker Screen, Maternal, Serum

Useful For
Suggests clinical disorders or settings where the test may be helpful

Prenatal screening for open neural tube defect

Highlights

This test is a screening assay to identify pregnancies that may have an increased risk for neural tube defects (NTD).

 

A screen-positive result indicates that the calculated alpha-fetoprotein multiple of the median (MoM) is 2.50 or greater and may indicate an increased risk for NTD.

 

A screen-positive result does not infer a definitive diagnosis of a NTD but indicates that further evaluation should be considered.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

Two-Site Immunoenzymatic (Sandwich) Assay

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

AFP Single Marker SCRN, Maternal, S

Aliases
Lists additional common names for a test, as an aid in searching

AFP Maternal Screening

AFP Neural Tube Defects

Maternal Screening, AFP Single Marker

Specimen Type
Describes the specimen type validated for testing

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 (AFP)/QUAD Screen Patient Information (T595).

ORDER QUESTIONS AND ANSWERS

Question ID Description Answers
DRPHN Physician Phone Number
MTWT Patient Weight
LBKGS Units (lbs or kg) lbs
kg
EGGDR IVF Egg Donor Date of Birth
EGGFR IVF Egg or Embryo Freeze Date
PRHIS Prev Down (T21) / Trisomy Pregnancy No
Yes
Unknown
If MAFP - Not applicable
IDD Insulin dependent diabetes None
Diabetic
RACE1 Patients race Black
non-Black
IVFP IVF pregnancy No
Yes
PRNTD Prev Pregnancy w/ Neural Tube Defect No
Yes
Unknown
PTNTD Patient or father of baby has a NTD No
Yes
Unknown
MULTF Number of Fetuses 1
2
3 or more
CHOR_ Number of Chorions Monochorionic
Dichorionic
Unknown
Not applicable
ESTDD Patient's Estimated Due Date (EDD)
MTHOD Method Used to Determine EDD Ultrasound
LMP
SMKNG Current Cigarette smoking status Non-smoker
Smoker
INTL Initial or repeat testing Initial
Repeat

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Container/Tube:

Preferred: Serum gel

Acceptable: Red Top

Specimen Volume: 1 mL

Collection Instructions:

1. Do not collect specimen after amniocentesis as this could affect results.

2. Centrifuge immediately.

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.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Forms

1. Second Trimester Maternal Screening Alpha-Fetoprotein (AFP)/QUAD Screen Patient Information (T595) is required; see Special Instructions.

2. If not ordering electronically, complete, print, and send a General Request (T239).

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia OK
Gross icterus OK

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
Frozen 90 days
Ambient 7 days

Useful For
Suggests clinical disorders or settings where the test may be helpful

Prenatal screening for open neural tube defect

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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 of the 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
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

NEURAL TUBE DEFECTS

An alpha-fetoprotein (AFP) multiple of the median (MoM) <2.5 is reported as screen negative.

AFP MoM > or =2.5 (singleton and twin pregnancies) are reported as screen positive.

 

An interpretive report will be provided.

Interpretation
Provides information to assist in interpretation of the test results

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.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Race, weight, smoking, multiple fetus pregnancy, and insulin-dependent diabetes (IDD) may affect marker concentrations. Black mothers tend to have higher alpha-fetoprotein (AFP) levels but lower risk of neural tube defects and are assigned to a separate AFP median set. Multiple of the medians (MoM) are adjusted for maternal weight (to account for dilution effects in heavier mothers). The AFP is adjusted upward in IDD to account for lower values in diabetic pregnancies. Smoking results in higher second trimester maternal serum AFP. MoM are adjusted accordingly to account for serum AFP differences in smokers.

 

The screen results are dependent on accurate information for gestation, race, IDD, and weight. Inaccurate information can lead to significant alterations in the estimated risk. In particular, erroneous assessment of gestational age can result in false-positive or false-negative screen results. Because of its increased accuracy, the determination of gestational age by ultrasound is recommended, when possible, rather than by last menstrual period.

 

A screen-negative result does not guarantee the absence of fetal defects. A screen-positive result does not provide a diagnosis but indicates that further diagnostic testing should be considered (an unaffected fetus may have screen-positive result for unknown reasons).

 

Valid measurements of AFP in maternal serum cannot be made after amniocentesis.

 

Triplet and higher multiple pregnancies cannot be interpreted.

 

Each center offering maternal serum screening to patients should establish a standard screening protocol, which provides pre- and post-screening education and appropriate follow-up for screen-positive results.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Christensen RL, Rea MR, Kessler G, et al: Implementation of a screening program for diagnosing open neural tube defects: selection, evaluation, and utilization of alpha-fetoprotein methodology. Clin Chem. 1986;32:1812-1817

2. American College of Obstetricians and Gynecologists: Practice Bulletin No. 163: Screening for Fetal Aneuploidy. Obstet Gynecol. 2016 May;127(5):e123-137

3. Zhang J, Lambert-Messerlian G, Palomaki GE, Canick JA: Impact of smoking on maternal serum markers and prenatal screening in the first and second trimesters. Prenat Diagn. 2011 Jun;31(6):583-588

4. Yarbrough ML, Stout M, Gronowski AM: Pregnancy and its disorders. In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:1655-1696

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Description
Describes how the test is performed and provides a method-specific reference

Alpha-fetoprotein (AFP) values are compared to the median value for the unaffected population at a given gestational age and the multiple of the median is obtained and classified as either screen-positive or screen-negative. The Access AFP assay is a 2-site immunoenzymatic sandwich assay. A sample is added to a reaction vessel with mouse monoclonal anti-AFP alkaline phosphatase conjugate and paramagnetic particles coated with a second mouse monoclonal anti-AFP antibody. The AFP in the sample binds to the immobilized monoclonal anti-AFP on the solid phase while, at the same time, the monoclonal anti-AFP-alkaline phosphatase conjugate reacts with different antigenic sites on the sample AFP. After incubation in a reaction vessel, materials bound to the solid phase are held in a magnetic field while unbound materials are washed away. Then the chemiluminescent substrate Lumi-Phos*530 is added to the reaction vessel and light generated by the reaction is measured with a luminometer. The light production is directly proportional to the amount of AFP in the sample. The amount of analyte in the sample is determined by means of a stored multipoint calibration curve.(Instruction manual: Beckman-Coulter Assay, Beckman Coulter, Inc. 2019)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

4 to 6 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

9 months

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

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
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

82105

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

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
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
IDD Insulin dependent diabetes 44877-9
IVFP IVF pregnancy 47224-1
MULTF Number of Fetuses 55281-0
10356 INTERPRETATION 49092-0
10248 Additional comments 48767-8
10357 RECOMMENDED FOLLOW UP 80615-8
10358 GENERAL TEST INFORMATION 62364-5
7058 Recalculated Maternal Serum Screen 32399-8
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
10054 EDD by U/S scan 11781-2
7753 EDD by LMP 11779-6
7203 GA on collection by U/S scan 11888-5
7204 GA on collection by dates 11885-1
7830 GA used in risk estimate 21299-3
10351 AFP 83073-7
113146 Results Summary 32399-8
113147 Neural tube defect risk estimate 48803-1
113148 AFP MoM 23811-3
RACE1 Patient race 21484-1
SMKNG Current cigarette smoking status 64234-8
CHOR_ Number of Chorions 92568-5
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

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports