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23214 Alpha-Fetoprotein, Amniotic Fluid (AFPA)

Alpha-Fetoprotein, Amniotic Fluid (AFPA)
Test Code: AFAFPSO
Synonyms/Keywords

AFP (Alpha-Fetoprotein); AFP-AF (Alpha-Fetoprotein, Amniotic Fluid); Alpha Fetoprotein, Amniotic Fluid; Alpha-Fetoprotein, Amniotic Fluid; Fetoprotein, Amniotic Fluid

Test Components

​If alpha-fetoprotein is positive, then acetylcholinesterase will be performed at an additional charge.

Useful For
​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
​
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)		 Pediatric Minimum Volume
(no repeat)
Amniotic fluid​ Amniotic fluid container​ ​ 0.75 mL​ 0.5 mL​ ​
Collection Processing Instructions

Do not centrifuge.  ​

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.
 
 
Specimen Stability Information
Specimen Type Temperature Time
Amniotic Fluid​ ​ Refrigerated​ (preferred) 7 days​
​Ambient​7 days
Rejection Criteria

​All specimens will be evaluated at Mayo Clinic Laboratories for test suitability. 

Interference

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.

Performing Laboratory Information
Performing Location Day(s) Test Performed Report Available Methodology/Instrumentation
Mayo Clinic Laboratories​
 Monday through Friday​
2  to 19 days​
AFPA: Immunoenzymatic Assay
ACHE_: Polyacrylamide Electrophoresis​
Reference Lab
Mayo Clinic Laboratories
Test Information

​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 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 Range Information
< 2.0 multiples of median (MoM)
Interpretation

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.

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. False-positive AChE may occur from a bloody tap, which may cause both elevated AFP and AChE levels

Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
​82106 ​ ​1 ​ ​
​82013 ​ ​1 ​Acetylcholinesterase ​If needed
Synonyms/Keywords

AFP (Alpha-Fetoprotein); AFP-AF (Alpha-Fetoprotein, Amniotic Fluid); Alpha Fetoprotein, Amniotic Fluid; Alpha-Fetoprotein, Amniotic Fluid; Fetoprotein, Amniotic Fluid

Test Components

​If alpha-fetoprotein is positive, then acetylcholinesterase will be performed at an additional charge.

Ordering Applications
Ordering Application Description
​Cerner ​Alpha-Fetoprotein, Amniotic Fluid (AFPA)
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)		 Pediatric Minimum Volume
(no repeat)
Amniotic fluid​ Amniotic fluid container​ ​ 0.75 mL​ 0.5 mL​ ​
Collection Processing

Do not centrifuge.  ​

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.
 
 
Specimen Stability Information
Specimen Type Temperature Time
Amniotic Fluid​ ​ Refrigerated​ (preferred) 7 days​
​Ambient​7 days
Rejection Criteria

​All specimens will be evaluated at Mayo Clinic Laboratories for test suitability. 

Interference

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.

Useful For
​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
​
Test Components

​If alpha-fetoprotein is positive, then acetylcholinesterase will be performed at an additional charge.

Reference Range Information
< 2.0 multiples of median (MoM)
Interpretation

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.

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. False-positive AChE may occur from a bloody tap, which may cause both elevated AFP and AChE levels

For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Report Available Methodology/Instrumentation
Mayo Clinic Laboratories​
 Monday through Friday​
2  to 19 days​
AFPA: Immunoenzymatic Assay
ACHE_: Polyacrylamide Electrophoresis​
Reference Lab
Mayo Clinic Laboratories
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
​82106 ​ ​1 ​ ​
​82013 ​ ​1 ​Acetylcholinesterase ​If needed
For most current information refer to the Marshfield Laboratory online reference manual.