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23216 Chromosome Analysis, Amniotic F (CHRAF)

Chromosome Analysis, Amniotic F (CHRAF)
Test Code: AFCASO
Synonyms/Keywords
Amniotic Fluid, Chromosome Analysis; Chromosome Analysis, Amniotic Fluid; Karyotype, Amniotic Fluid; Prenatal Chromosomes, Amniotic Fluid; Fetal Aneuploidy; Fetal Chromosome Analysis; DNA Screening for Fetal Aneuploidy
Useful For
Prenatal diagnosis of chromosome abnormalities, including aneuploidy (ie, trisomy or monosomy) and balanced rearrangements
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​ Centrifuge Tube​ ​20-25 mL 12 mL​
​Fetal body fluid ​Sterile Tube ​Entire Specimen ​N/A
Collection Processing Instructions

​Amniotic Fluid:

1. Optimal timing for specimen collection is during 14 to 18 weeks of gestation, but specimens collected at other weeks of gestation are also accepted.
2. Discard the first 2 mL of amniotic fluid.
Additional Information:
1. Place the tube in a Styrofoam container (Supply T329). Fill remaining space with packing material.
2. Unavoidably, about 1% to 2% of mailed-in specimens are not viable. If the specimen does not grow in culture, you will be notified within 7 days of receipt.
3. Bloody specimens are undesirable.
 
Fetal body fluid:
1. Place the tube in a Styrofoam container (Supply T329). Fill remaining space with packing material.
2. If the specimen does not grow in culture, you will be notified within 7 days of receipt.
3. Clearly indicate on tube and paperwork that specimen is fetal body fluid.
 
Necessary Information:
Provide a reason for referral and gestational age with each specimen, and verify the specimen source. The laboratory will not reject testing if this information is not provided, but appropriate testing and interpretation may be compromised or delayed.
Specimen Stability Information
Specimen Type Temperature
​Amniotic Fluid ​ ​Refrigerated (preferred)
​Ambient
Rejection Criteria

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

Interference

​Interfering factors:

-Improper syringes or transport vessels may be unsuitable to amniotic cells. Amniotic fluid should not be exposed to the syringe plunger tip for longer than a few seconds and fluid should be transferred to a transport (centrifuge) tube as soon as possible following collection.

-Transport time should not exceed 2 days.

-A bloody specimen may interfere with attempts to culture cells and contamination by maternal cells may cause interpretive problems.

-Inadequate amount of fluid may not permit adequate analysis.

-Improper packaging may result in broken, leaky, and contaminated specimen during transport.

-Exposure of the specimen to temperature extremes (freezing or >30 degrees C) may kill cells and severely interferes with attempts to culture cells.

Performing Laboratory Information
Performing Location Day(s) Test Performed Report Available Methodology/Instrumentation

Mayo Clinic Laboratories​

Monday through Friday
10 to 11 days​
Cell Culture Followed by Chromosome Analysis
Reference Lab
Test Information

Chromosome analysis for prenatal diagnosis is appropriate in pregnancies with abnormal maternal screening, advanced maternal age, and features suggestive of or concerns for aneuploidy syndromes, including Down syndrome, Turner syndrome, Klinefelter syndrome, trisomy 13 syndrome, and trisomy 18 syndrome.

Chromosomal abnormalities are the cause of a wide range of disorders associated with birth defects and congenital diseases. Many of these disorders can be diagnosed prenatally by analysis of amniocytes. This method permits diagnosis of chromosome abnormalities during the second trimester of pregnancy or later.

A chromosomal microarray (CMAP / Chromosomal Microarray, Prenatal, Amniotic Fluid/Chorionic Villus Sampling) is recommended, rather than chromosomal analysis, to detect clinically relevant gains or losses of chromosomal material in pregnancies with 1 or more major structural abnormalities. Chromosomal microarray can also be considered, rather than chromosome analysis, for patients undergoing invasive prenatal diagnostic testing with a structurally normal fetus.

Reference Range Information
An interpretative report will be provided.
Interpretation
Cytogenetic studies on amniotic fluid are considered nearly 100% accurate for the detection of large fetal chromosome abnormalities. However, subtle or cryptic abnormalities involving microdeletions usually can be detected only with the use of targeted FISH testing.
 
Approximately 3% of amniotic fluid specimens analyzed are found to have chromosome abnormalities. Some of these chromosome abnormalities are balanced and may not be associated with birth defects.
 
A normal karyotype does not rule out the possibility of birth defects, such as those caused by submicroscopic cytogenetic abnormalities, molecular mutations, and other environmental factors (ie, teratogen exposure). For these reasons, clinicians should inform their patients of the technical limitations of chromosome analysis prior to performing the amniocentesis.
 
It is recommended that a qualified professional in Medical Genetics communicate all results to the patient. 
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
​88291

​1

​Interpretation and report
​88235 ​2 ​Culture 03
​88267 ​1 ​Metaphases, <15 ​If needed
​88267 ​1 ​Metaphases, 15 ​If needed
​88267 ​2 ​Metaphases, >15 ​If needed
​88285 ​1 ​Metaphases, >15 ​If needed
​88269 ​1 ​Colonies, 1-5 ​If needed
​88269 ​1 ​Colonies, 6+ ​If needed
​88283 ​1 ​Ag-Nor/CBL Stain ​If needed
​88280 ​1 ​Karyotypes, >1 ​If needed
Synonyms/Keywords
Amniotic Fluid, Chromosome Analysis; Chromosome Analysis, Amniotic Fluid; Karyotype, Amniotic Fluid; Prenatal Chromosomes, Amniotic Fluid; Fetal Aneuploidy; Fetal Chromosome Analysis; DNA Screening for Fetal Aneuploidy
Ordering Applications
Ordering Application Description
​Centricity ​Amnio Chromosome Analysis
​Cerner ​Chromosome Analysis, Amniotic Fluid (AF)
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​ Centrifuge Tube​ ​20-25 mL 12 mL​
​Fetal body fluid ​Sterile Tube ​Entire Specimen ​N/A
Collection Processing

​Amniotic Fluid:

1. Optimal timing for specimen collection is during 14 to 18 weeks of gestation, but specimens collected at other weeks of gestation are also accepted.
2. Discard the first 2 mL of amniotic fluid.
Additional Information:
1. Place the tube in a Styrofoam container (Supply T329). Fill remaining space with packing material.
2. Unavoidably, about 1% to 2% of mailed-in specimens are not viable. If the specimen does not grow in culture, you will be notified within 7 days of receipt.
3. Bloody specimens are undesirable.
 
Fetal body fluid:
1. Place the tube in a Styrofoam container (Supply T329). Fill remaining space with packing material.
2. If the specimen does not grow in culture, you will be notified within 7 days of receipt.
3. Clearly indicate on tube and paperwork that specimen is fetal body fluid.
 
Necessary Information:
Provide a reason for referral and gestational age with each specimen, and verify the specimen source. The laboratory will not reject testing if this information is not provided, but appropriate testing and interpretation may be compromised or delayed.
Specimen Stability Information
Specimen Type Temperature
​Amniotic Fluid ​ ​Refrigerated (preferred)
​Ambient
Rejection Criteria

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

Interference

​Interfering factors:

-Improper syringes or transport vessels may be unsuitable to amniotic cells. Amniotic fluid should not be exposed to the syringe plunger tip for longer than a few seconds and fluid should be transferred to a transport (centrifuge) tube as soon as possible following collection.

-Transport time should not exceed 2 days.

-A bloody specimen may interfere with attempts to culture cells and contamination by maternal cells may cause interpretive problems.

-Inadequate amount of fluid may not permit adequate analysis.

-Improper packaging may result in broken, leaky, and contaminated specimen during transport.

-Exposure of the specimen to temperature extremes (freezing or >30 degrees C) may kill cells and severely interferes with attempts to culture cells.

Useful For
Prenatal diagnosis of chromosome abnormalities, including aneuploidy (ie, trisomy or monosomy) and balanced rearrangements
Reference Range Information
An interpretative report will be provided.
Interpretation
Cytogenetic studies on amniotic fluid are considered nearly 100% accurate for the detection of large fetal chromosome abnormalities. However, subtle or cryptic abnormalities involving microdeletions usually can be detected only with the use of targeted FISH testing.
 
Approximately 3% of amniotic fluid specimens analyzed are found to have chromosome abnormalities. Some of these chromosome abnormalities are balanced and may not be associated with birth defects.
 
A normal karyotype does not rule out the possibility of birth defects, such as those caused by submicroscopic cytogenetic abnormalities, molecular mutations, and other environmental factors (ie, teratogen exposure). For these reasons, clinicians should inform their patients of the technical limitations of chromosome analysis prior to performing the amniocentesis.
 
It is recommended that a qualified professional in Medical Genetics communicate all results to the patient. 
For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Report Available Methodology/Instrumentation

Mayo Clinic Laboratories​

Monday through Friday
10 to 11 days​
Cell Culture Followed by Chromosome Analysis
Reference Lab
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
​88291

​1

​Interpretation and report
​88235 ​2 ​Culture 03
​88267 ​1 ​Metaphases, <15 ​If needed
​88267 ​1 ​Metaphases, 15 ​If needed
​88267 ​2 ​Metaphases, >15 ​If needed
​88285 ​1 ​Metaphases, >15 ​If needed
​88269 ​1 ​Colonies, 1-5 ​If needed
​88269 ​1 ​Colonies, 6+ ​If needed
​88283 ​1 ​Ag-Nor/CBL Stain ​If needed
​88280 ​1 ​Karyotypes, >1 ​If needed
For most current information refer to the Marshfield Laboratory online reference manual.