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Test ID: CMACB Chromosomal Microarray, Congenital, Blood

Useful For

First-tier, postnatal test for individuals with multiple anomalies that are not specific to well-delineated genetic syndromes, apparently nonsyndromic developmental delay or intellectual disability, or autism spectrum disorders as recommended by the American College of Medical Genetics (ACMG)

 

An appropriate follow-up test for individuals with unexplained developmental delay or intellectual disability, autism spectrum disorders, or congenital anomalies with a previously normal conventional chromosome study

 

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 identity by descent

Method Name

Chromosomal Microarray (CMA) Using Affymetrix Cytoscan HD

Reporting Name

Chromosomal Microarray, Blood

Specimen Type

Whole blood


Shipping Instructions


Specimens must arrive within 96 hours of draw.



Necessary Information


The reason for referral is required.



Specimen Required


This test requires 2 blood specimens: 1 sodium heparin and 1 EDTA.

Specimen Type: Whole blood

Container/Tube: Green top (sodium heparin) and lavender top (EDTA)

Specimen Volume: 3 mL EDTA tube and 4 mL sodium heparin tube

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimens in original tubes.

Additional Information: As a participant in the International Standard Cytogenomic Array Consortium, patients may request to opt-out. See Chromosomal Microarray Testing and the ISCA Consortium Database patient education flyer under Special Instructions.


Specimen Minimum Volume

2 mL

Specimen Stability Information

Specimen Type Temperature Time
Whole blood Ambient (preferred)
  Refrigerated 

Clinical Information

Aneuploidy or unbalanced chromosome rearrangements are often found in patients with intellectual disability, developmental delay, autism, dysmorphic features, or congenital anomalies. Some chromosomal abnormalities are large enough to be detected with conventional chromosome analysis. However, many pathogenic rearrangements are below the resolution limits of chromosome analysis (approximately 5 megabases). Chromosomal microarray (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 greater than 1.9 million copy number probes and approximately 750,000 single nucleotide polymorphism probes for the detection of copy number changes and regions of excessive homozygosity. Identification of regions of excessive homozygosity on a single chromosome could suggest uniparental disomy (UPD), which may warrant further clinical investigation when observed on chromosomes with known imprinting disorders associated with UPD. In addition, the detection of excessive homozygosity on multiple chromosomes may suggest consanguinity and, therefore, could be useful in determining candidate genes for further testing for autosomal recessive disorders.

 

As a participant in the International Standard Cytogenomic Array Consortium (ISCA) (see Chromosomal Microarray Testing and the ISCA Consortium Database in Special Instructions), Mayo Clinic Cytogenetics Laboratory contributes submitted clinical information and test results for molecular cytogenetic tests to a HIPAA-compliant, deidentified public database hosted by the National Institute of Health. This is an international effort to improve diagnostic testing and our understanding of the relationships between genetic changes and clinical symptoms (for information about the database visit the consortium website at https://www.iscaconsortium.org). Confidentiality of each specimen is maintained. Patients may request to opt-out of this scientific effort by calling the laboratory at 800-533-1710, extension 4-1668, and asking to speak with a laboratory genetic counselor. Please call with any questions.

 

An online research opportunity called GenomeConnect (genomeconnect.org) is available for the recipients of genetic test results. This patient registry collects deidentified genetic and health information to advance knowledge of genetic variants. See GenomeConnect Patient Portal in Special Instructions for more information.

Reference Values

An interpretive report will be provided.

Interpretation

When interpreting results, the following factors need to be considered:

Copy number variation is found in all individuals, including patients with abnormal phenotypes and normal populations. Therefore, determining the clinical significance of a rare or novel copy number change can be challenging. Parental testing may be necessary to further assess the potential pathogenicity of a copy number change.

 

While most 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. In these situations, a number of considerations are taken into account to help interpret results including the size and gene content of the imbalance, whether the change is a deletion or duplication, the inheritance pattern, and the clinical and/or developmental history of a transmitting parent.

 

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 excessive 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 consistent with the patient's clinical presentation that are present in regions of homozygosity.

 

Families benefit from hearing genetic information multiple times and in multiple ways. A referral to a clinical genetics professional is appropriate for individuals and families to discuss the results of chromosomal microarray testing.

Clinical Reference

1. Manning M, Hudgins L: Professional Practice and Guidelines Committee: Array-based technology and recommendations for utilization in medical genetics practice for detection of chromosomal abnormalities. Genet Med 2010;12(11):742-745

2. Miller DT, Adam MP, Aradhya S, et al: Consensus statement: Chromosomal microarray is a first-tier clinical diagnostic test for individuals with developmental disabilities or congenital anomalies. Am J Hum Genet 2010;86:749-764

3. Kearney HM, Thorland EC, Brown KK, et al: American College of Medical Genetics standards and guidelines for interpretation and reporting of postnatal constitutional copy number variants. Genet Med 2011;13(7)680-685

4. Kearney HM, Kearney JB, Conlin LK: Diagnostic implications of excessive homozygosity detected by SNP-based microarrays: consanguinity, uniparental disomy, and recessive single-gene mutations. Clin Lab Med 2011;31(4):595-613

Day(s) and Time(s) Performed

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

Analytic Time

8 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
CMACB Chromosomal Microarray, Blood In Process

 

Result ID Test Result Name Result LOINC Value
52399 Result Summary 50397-9
52400 Result In Process
54643 Nomenclature In Process
52401 Interpretation In Process
CG779 Reason For Referral 42349-1
54713 Specimen 31208-2
52402 Source 31208-2
52403 Method 49549-9
55128 Additional Information 48767-8
52404 Released By No LOINC Needed

Testing Algorithm

This test is not appropriate for detecting acquired copy number changes and excessive homozygosity. If this test is ordered with a reason for referral indicating a hematological disorder, the test will be cancelled and CMAH / Chromosomal Microarray, Hematologic Disorders will be performed as the appropriate test.

Forms

1. 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.

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

3. If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/neurology-request-form.pdf)

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

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