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Test ID: CMAPC Chromosomal Microarray, Autopsy, Products of Conception, or Stillbirth

Useful For

Prenatal diagnosis of copy number changes (gains or losses) across the entire genome

 

Diagnosing chromosomal causes for fetal death

 

Determining recurrence risk of future pregnancy losses

 

Determining the size, precise breakpoints, gene content, and any unappreciated complexity of abnormalities detected by other methods such as conventional chromosome and FISH studies

 

Determining if apparently balanced abnormalities identified by previous conventional chromosome studies have cryptic imbalances, since a proportion of such rearrangements that appear balanced at the resolution of a chromosome study are actually unbalanced when analyzed by higher-resolution chromosomal microarray

 

Assessing regions of homozygosity related to uniparental disomy or identical by descent

Testing Algorithm

A maternal blood sample is requested when ordering this test (see PPAP / Parental Sample Prep for Prenatal Microarray Testing); the PPAP test must be ordered under a different order number than the prenatal specimen.

 

Maternal cell contamination (MCC) testing will be performed at no additional charge on the maternal blood and fetal tissue to rule out the presence of maternal cells in the product of conception sample.

 

A paternal blood sample is desired but not required (see PPAP / Parental Sample Prep for Prenatal Microarray Testing).

 

If an insufficient sample is received or MCC is identified in the prenatal sample, microarray testing will be performed on cultured material.

 

The following algorithms are available in Special Instructions:

-Prenatal Aneuploidy Screening and Diagnostic Testing Options

-High-Risk Pregnancy Based on Abnormal Fetal Malformations: Laboratory Testing Algorithm

Method Name

Chromosomal Microarray (CMA) Using Affymetrix Cytoscan HD

Reporting Name

Chromosomal Microarray, POC

Specimen Type

Varies


Advisory Information


This test does not detect balanced chromosome rearrangements such as Robertsonian or other reciprocal translocations, inversions, or balanced insertions. These abnormalities may be identified by chromosome analysis (see CHRPC / Chromosome Analysis, Autopsy, Products of Conception, or Stillbirth).



Additional Testing Requirements


A maternal blood sample is requested when ordering this test (see PPAP / Parental Sample Prep for Prenatal Microarray Testing); the PPAP test must be ordered under a different order number than the prenatal specimen.

 

A paternal blood sample is desired but not required (see PPAP / Parental Sample Prep for Prenatal Microarray Testing).

 

If additional molecular genetic or biochemical genetic testing is needed, order CULAF / Amniotic Fluid Culture for Genetic Testing or CULFB / Fibroblast Culture for Genetic Testing so that cultures may be set up specifically for use in these tests.



Shipping Instructions


Advise Express Mail or equivalent if not on courier service.



Necessary Information


1. Provide a reason for referral with each specimen. The laboratory will not reject testing if this information is not provided, but appropriate testing and interpretation may be compromised or delayed.

2. Notify the laboratory if the pregnancy involves an egg donor or gestational carrier.



Specimen Required


Submit only 1 of the following specimens:

 

Supplies: Hank's Solution (T132)

Specimen Type: Products of conception or stillbirth

Container/Tube: Sterile container with sterile Hank's solution (T132), Ringer's solution, or normal saline

Specimen Volume: 1 cm(3) of placenta (including 50-mg chorionic villi) and 1 cm(3) biopsy specimen of muscle/fascia from the thigh

Collection Instructions:

1. Attempt to identify and send only fetal tissue for analysis.

2. If a fetus cannot be specifically identified, collect 50-mg villus material or tissue that appears to be of fetal origin.

3. If multiple specimen types are sent, send each specimen in a separate container. Multiple specimens received (eg, placenta and fetal thigh) will be ordered under 1 test. All specimens will be processed separately.

Additional Information:

1. Do not send entire fetus.

2. While fresher specimens prepared as described above are preferred, we can attempt analysis on specimens that have been in less-than-ideal conditions.

 

Supplies: Hank's Solution (T132)

Specimen Type: Autopsy

Container/Tube: Sterile container with sterile Hank's solution (T132), Ringer's solution, or normal saline

Specimen Volume: 1 cm(3) biopsy specimen of muscle/fascia from the thigh

Collection Instructions:

1. Wash biopsy site with an antiseptic soap.

2. Thoroughly rinse area with sterile water.

3. Do not use alcohol or iodine preparations.

4. Biopsy specimens are best taken by punch biopsy to include full thickness of dermis.

 

Supplies: Refrigerate/Ambient Mailer, 5 lb (T329)

Specimen Type: Amniotic fluid

Container/Tube: Amniotic fluid container

Specimen Volume: 20-30 mL

Collection Instructions:

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. Provide gestational age at the time of amniocentesis.

2. Discard the first 2 mL of amniotic fluid.

3. Place the tubes in a Refrigerate/Ambient Mailer, 5 lb (T329).

4. Fill remaining space with packing material.

Additional Information:

1. Unavoidably, about 1% to 2% of mailed-in specimens are not viable.

2. Bloody specimens are undesirable.

3. Results will be reported and also telephoned or faxed, if requested.

 

Supplies: CVS Media (RPMI) and Small Dish (T095)

Specimen Type: Chorionic villus

Container/Tube: 15-mL tube containing 15 mL of transport media

Specimen Volume: 50 mg

Collection Instructions:

1. Collect chorionic villus specimen (CVS) by transabdominal or transcervical method.

2. Transfer CVS to a Petri dish containing transport medium (Such as CVS Media [RPMI] and Small Dish [T095]).

3. Using a stereomicroscope and sterile forceps, assess the quality and quantity of villi and remove any blood clots and maternal decidua.

 

Acceptable

Specimen Type: Cultured cells

Container/Tube: T225 flasks with culture media

Specimen Volume: 2 T225 flasks

 

Supplies: Hank Solution (T132)

Specimen Type: Tissue

Container/Tube: In sterile Hank's solution (T132)


Specimen Minimum Volume

Chorionic Villus: 10 mg
Muscle-Fascia: 1 cm(3)

Specimen Stability Information

Specimen Type Temperature Time
Varies Ambient (preferred)
  Refrigerated 

Clinical Information

Chromosomal abnormalities may result in malformed fetuses, spontaneous abortions, or neonatal deaths. Estimates of the frequency of chromosome abnormalities in spontaneously aborted fetuses range from 15% to 60%.

 

Chromosomal microarray (CMA) studies of products of conception (POC), a stillborn infant, or neonate (autopsy) may provide useful information concerning the cause of fetal loss. In addition, CMA may provide information regarding the recurrence risk for future pregnancy loss and risk of having subsequent children with chromosome anomalies. This is particularly useful information if there is a family history of 2 or more miscarriages or when fetal malformations are evident.

 

CMA is a high-resolution method for detecting copy number changes (gains or losses) across the entire genome in a single assay and is sometimes called a molecular karyotype.

 

This CMA test utilizes more than 1.9 million copy number probes and approximately 750,000 single nucleotide polymorphism probes for the detection of copy number changes and regions with absence of heterozygosity. Identification of regions of excess homozygosity on a single chromosome could suggest uniparental disomy that may warrant further clinical investigation when observed on chromosomes with known imprinting disorders. In addition, the detection of excess homozygosity on multiple chromosomes may suggest consanguinity.

Reference Values

An interpretive report will be provided.

Interpretation

Copy number variants are classified based on known, predicted, or possible pathogenicity and reported with interpretive comments detailing their potential or known significance.

 

While many copy number changes observed by chromosomal microarray testing can readily be characterized as pathogenic or benign, there are limited data available to support definitive classification of a subset into either of these categories, making interpretation of these variants challenging. In these situations, a number of considerations are taken into account to help interpret results including the size and gene content of the imbalance, as well as whether the change is a deletion or duplication. Parental testing may also be necessary to further assess the potential pathogenicity of a copy number change. In such situations, the inheritance pattern and clinical and developmental history of the transmitting parent will be taken into consideration.

 

The continual discovery of novel copy number variation and published clinical reports means that the interpretation of any given copy number change may evolve with increased scientific understanding. The detection of excess homozygosity may suggest the need for additional clinical testing to confirm uniparental disomy or to test for mutations in genes associated with autosomal recessive disorders present in regions of homozygosity.

Clinical Reference

1. American College of Obstetricians and Gynecologists Committee on Genetics: Committee Opinion No. 581: the use of chromosomal microarray analysis in prenatal diagnosis. Obstet Gynecol 2013;122:1374-1377

2. Society for Maternal-Fetal Medicine (SMFM): The use of chromosomal microarray for prenatal diagnosis. Am J Obstet Gynecol  2016;215:B2-B9

3. Sahoo T, Dzidic N, Strecker MN, et al: Comprehensive genetic analysis of pregnancy loss by chromosomal microarrays: outcomes, benefits, and challenges. Genet Med 2017 Jan;19(1):83-89 doi: 10.1038/gim.2016.69

4. Rosenfeld JA, Tucker ME, Escobar LF, et al: Diagnostic utility of microarray testing in pregnancy loss. Ultrasound Obstet Gynecol 2015;46:478-486

Day(s) and Time(s) Performed

Samples processed Monday through Sunday. Results reported Monday through Friday, 8 a.m.-5 p.m.

Analytic Time

21 days

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

81229

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CMAPC Chromosomal Microarray, POC In Process

 

Result ID Test Result Name Result LOINC Value
55253 Result Summary 50397-9
55254 Result In Process
55255 Nomenclature 48767-8
55256 Interpretation 69965-2
CG945 Reason for Referral 42349-1
CG946 Specimen 31208-2
55257 Source 31208-2
55258 Method 49549-9
55259 Additional Information 48767-8
55260 Released By No LOINC Needed

Forms

1. Chromosomal Microarray Patient Information (T665) in Special Instructions

2. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

3. Final Disposition of Fetal/Stillborn Remains form (if fetal specimen is sent) in Special Instructions (Only for products of conception or stillbirth specimen).

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

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