Test Id : AFPA
Alpha-Fetoprotein, Amniotic Fluid
Useful For
Suggests clinical disorders or settings where the test may be helpful
Screening for open neural tube defects or other fetal abnormalities
Follow-up testing for patients with elevated serum alpha-fetoprotein results or in conjunction with cytogenetic testing
Reflex Tests
Lists tests that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial tests.
| Test Id | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| ACHE_ | Acetylcholinesterase, AF | Yes | No |
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
If alpha-fetoprotein is positive, then acetylcholinesterase will be performed at an additional charge.
Method Name
A short description of the method used to perform the test
AFPA: Immunoenzymatic Assay
ACHE_: Polyacrylamide Electrophoresis
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
AFP (Alpha-Fetoprotein)
AFP-AF (Alpha-Fetoprotein, Amniotic Fluid)
Alpha Fetoprotein, Amniotic Fluid
Alpha-Fetoprotein, Amniotic Fluid
Fetoprotein, Amniotic Fluid
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
If alpha-fetoprotein is positive, then acetylcholinesterase will be performed at an additional charge.
Specimen Type
Describes the specimen type validated for testing
Amniotic Fld
Necessary Information
The following information is required:
1. Estimated due date by ultrasound
2. Collection date
3. Gestational age must be between 13 and 24 weeks; 16 to 18 weeks preferred.
If not ordering electronically, provide information on Second Trimester Maternal Screening Alpha-Fetoprotein / Quad Screen Patient Information (T595) and send with specimen.
ORDER QUESTIONS AND ANSWERS
| Question ID | Description | Answers |
|---|---|---|
| DRPN1 | Physician Phone Number | |
| DAT15 | EDD by US Scan |
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Container/Tube: Plain, plastic, screw-top tube
Specimen Volume: 0.75 mL
Collection Instructions: Do not centrifuge.
Special Instructions
Library of PDFs including pertinent information and forms related to the test
Forms
Second Trimester Maternal Screening Alpha-Fetoprotein / Quad Screen Patient Information (T595) is required.
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
0.5 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
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 |
|---|---|---|---|
| Amniotic Fld | Refrigerated (preferred) | 7 days | |
| Ambient | 7 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
Screening for open neural tube defects or other fetal abnormalities
Follow-up testing for patients with elevated serum alpha-fetoprotein results or in conjunction with cytogenetic testing
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
If alpha-fetoprotein is positive, then acetylcholinesterase will be performed at an additional charge.
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Alpha-fetoprotein (AFP) is a single polypeptide chain glycoprotein with a molecular weight of approximately 70,000 Da. Synthesis of AFP occurs primarily in the liver and yolk sac of the fetus. It is secreted in fetal serum, reaching a peak at approximately 13 weeks gestation, after which it rapidly declines until about 22 weeks gestation and then gradually declines until term. Transfer of AFP into maternal circulation is accomplished primarily through diffusion across the placenta. Maternal serum AFP levels rise from the normal non-pregnancy level of 0.20 ng/mL to about 250 ng/mL at 32 weeks gestation.
If the fetus has an open neural tube defect, AFP is thought to leak directly into the amniotic fluid, causing unexpectedly high concentrations of AFP. Other fetal abnormalities such as omphalocele, gastroschisis, congenital kidney disease, and esophageal atresia; and other fetal distress situations such as threatened abortion, prematurity, and fetal demise, may also show AFP elevations. Decreased amniotic fluid AFP values may be seen when gestational age has been overestimated.
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.
< 2.0 multiples of median (MoM)
Interpretation
Provides information to assist in interpretation of the test results
A screening alpha-fetoprotein (AFP) cutoff level of 2.0 multiples of median (MoM), followed by acetylcholinesterase (AChE) confirmatory testing on positive results, is capable of detecting 96% of open spina bifida cases with a false-positive rate of only 0.06% in non-blood-stained specimens.
Acetylcholinesterase analysis is an essential confirmatory test for all amniotic fluid specimens with positive AFP results. Normal amniotic fluid does not contain AChE, unless contributed by the fetus as a result of open communication between fetal central nervous system (eg, open neural tube defects) or, to a lesser degree, fetal circulation. All amniotic fluid specimens testing positive for AFP will have the AChE test performed. False-positive AChE may occur from a bloody tap, which may cause both elevated AFP and AChE levels.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This test is for screening only.
Increases in alpha-fetoprotein (AFP) are not specific for neural tube defects, and the test must be used in combination with other procedures, such as ultrasonography and acetylcholinesterase measurements.
Elevated AFP levels also can be caused by benign factors and incorrect gestational dating.
Negative results do not guarantee the absence of defects.
In rare cases, some individuals can develop antibodies to mouse or other animal antibodies (often referred to as human anti-mouse antibodies [HAMA] or heterophile antibodies), which may cause interference in some immunoassays. Caution should be used in interpretation of results, and the laboratory should be alerted if the result does not correlate with the clinical presentation.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Clinical Laboratory Standards Institute (CLSI): Maternal Serum Screening: Approved Standard. 2nd ed. I/LA25-A2 CLSI; 2011
2. Cuckle H. Prenatal screening using maternal markers. J Clin Med. 2014;3(2):504-520. doi:10.3390/jcm3020504
3. Bernard JP, Cuckle HS, Bernard MA, Brochet C, Salomon LJ, Ville Y. Combined screening for open spina bifida at 11-13 weeks using fetal biparietal diameter and maternal serum markers. Am J Obstet Gynecol. 2013;209(3):223.e1-5
Method Description
Describes how the test is performed and provides a method-specific reference
The Access AFP (alpha-fetoprotein) 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. The chemiluminescent substrate Lumi-Phos530 is added to the reaction vessel and light generated by the reaction is measured by 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 multipoint calibration curve.(Package insert: Access AFP. Beckman Coulter Inc; 12/2021)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
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.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
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 account representative. 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.
CPT codes are provided by the performing laboratory.
82106
82013 (if appropriate)
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 |
|---|---|---|
| AFPA | Alpha Fetoprotein, AF | 58735-2 |
| 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.
|
|---|---|---|
| 6739 | Collection Date | 58734-5 |
| 6740 | Last Menstrual Period (LMP) | 8665-2 |
| 24233 | EDD by LMP | 11779-6 |
| 24239 | GA at Collection by Scan | 11888-5 |
| 24240 | GA at Collection by Dates | 11885-1 |
| 24234 | GA Used | 21299-3 |
| 24241 | Results | 29595-6 |
| 24235 | Interpretation | 59462-2 |
| 24236 | Additional Comments | 48767-8 |
| 24237 | Follow up | 80615-8 |
| 24238 | General Test Info | 48767-8 |
| 9950 | Alpha Fetoprotein, AF | 1832-5 |
| DAT15 | EDD by US Scan | 11781-2 |