Test ID: AFPA
Alpha-Fetoprotein, Amniotic Fluid
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
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 test(s) that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial test(s)
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| ACHE_ | Acetylcholinesterase, AF | Yes | No |
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
If alpha-fetoprotein (AFP) is positive, then acetylcholinesterase (AChE) will be performed at an additional charge. Because false-positive AChE may occur from a bloody tap, specimens with positive AChE results will also be tested for the presence of fetal hemoglobin at no additional charge.
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
AFPA/9950: Immunoenzymatic Assay
ACHE_/9287: Polyacrylamide Electrophoresis
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
AFP-AF (Alpha-Fetoprotein, Amniotic Fluid)
Alpha Fetoprotein, Amniotic Fluid
Alpha-Fetoprotein, Amniotic Fluid
Fetoprotein, Amniotic Fluid
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Container/Tube: Amniotic fluid container
Specimen Volume: 1 mL
Collection Instructions: Do not centrifuge.
Additional Information:
1. The following information is required:
a. Date ultrasound performed
b. Estimated due date by ultrasound
c. Collection date
d. Gestational age must be between 13 and 24 weeks; 16 to 18 weeks preferred.
2. If chromosome studies are also requested, see AF/8426 Chromosome Analysis, Amniotic Fluid. The specimen for AFP-AF testing, when requested with chromosome analysis, cannot be frozen.
Forms:
1. Second Trimester Maternal Screening Alpha-Fetoprotein (AFP)/QUAD Screen Patient Information Sheet (Supply T595) is required in Special Instructions
2. If not ordering electronically, submit a Cytogenetics/AFP Congenital Disorders Request Form (Supply T238) with the specimen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Amniotic Fld | Refrigerated | 7 days |
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 daltons. 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 nonpregnancy 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 renal 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.
< or =2.0 multiples of median (MoM)
Interpretation Provides information to assist in interpretation of the test results
A diagnostic 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.
AChE 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. Because false-positive AChE may occur from a bloody tap, specimens with positive AChE results will also be tested for the presence of fetal hemoglobin, 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.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
Assessing the Quality of Systems for Alpha-Fetoprotein (AFP) Assays Used in Prenatal Screening and Diagnosis of Open Neural Tube Defects: Approved Guideline. NCCLS I/LA17-A Vol 17. No 5. April 1997
Method Description Describes how the test is performed and provides a method-specific reference
Performed on the Beckman Coulter Unicel DxI 800, the Access AFP assay is a 2-site immunoenzymatic ("sandwich") assay. A sample is added to a reaction vessel with mouse monoclonal anti-alpha-fetoprotein (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-Phos*530 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. (Beckman-Coulter Assay Manual Beckman Coulter Inc., Fullerton, CA, 2010)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 5 a.m.-5 p.m., Saturday; 6 a.m.-1 p.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
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 The location of the laboratory that performs the test
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's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
82106-AFP
82013-Acetylcholinesterase (if appropriate)
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 6739 | Collection Date | 33882-2 |
| DAT15 | EDD by US Scan | N/A |
| 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 |
| 9950 | Alpha Fetoprotein, AF | 43798-8 |
| 24241 | Results | 43798-8 |
| 24235 | Interpretation | 59462-2 |
| 24236 | Additional Comments | 55107-7 |
| 24237 | Follow up | In Process |
| 24238 | General Test Info | In Process |
External
link
PDF
document
Excel
document
Word
document