Testing for Developmental Diseases

According to a recent article in Genetic Engineering & Biotechnology News, cytogenetic tests for developmental diseases tests allow identification of potential medical interventions for the patient, and enables accurate recurrence-risk counseling and helps families plan for the expected natural history of the disease.

One test specifically, cytogenomic microarray analysis (CMA), is a novel diagnostic tool for individuals with unexplained developmental delay, autism spectrum disease, and mental retardation. aCGH is used in addition to clinical evaluation and conventional genetic testing. For chromosomal microarray testing, highly specific oligonucleotide probes are designed and distributed throughout the genome, allowing for a whole genome survey in a single assay with very high resolution analysis.

In this fluorescence in situ hybridization image, 2 green control probes are present, indicating chromosome 22. The missing red signal demonstrates the 22q11.2 microdeletion on 1 homologue. Green = control probe; Red = 22q11.2 probe

According to the Mayo Clinic, CMA has quickly moved from research to the clinical setting and has emerged as the recommended first-tier postnatal test for individuals with multiple anomalies not specific to a well-delineated genetic syndrome, apparently nonsyndromic developmental delay/intellectual disability, and autism spectrum disorder.

As discussed in the Mayo Clinic communique, “Clinical Utility of Chromosomal Microarray Testing,” the interpretation of chromosomal microarray test results is a “complex and evolving process that is aided by collaboration between the clinician and clinical laboratory, particularly regarding the submission of detailed clinical information at the time of test referral. A genetic consultation is often of benefit to ensure the appropriate clinical interpretation of chromosomal microarray test results.” It also discusses how the rapid proliferation of array-based technology into clinical laboratories has led to a lack of uniform guidelines for the clinical interpretation of observed copy number variations, at times causing confusing results or conflicting reports between laboratories.

Duplicated region of chromosome 18, which is present on chromosome 2p due to an insertional translocation Green = 18 centromere, Red = 18q23
Duplicated region of chromosome 18, which is present on chromosome 2p due to an insertional translocation Green = 18 centromere, Red = 18q23

To address these issues, the International Standards for Cytogenomic Arrays (ISCA) Consortium, now consisting of about 160 international laboratories, including the Mayo Clinic, was formed with the goals of developing evidence-based standards for chromosomal microarray design, to build a public database of clinical array data as a resource for the clinical and research communities, and to utilize the database to develop standards and guidelines for the interpretation of copy number changes in the clinical setting.

For more information, read the full article.

Kelley Luedke

Kelley Luedke

Kelley Luedke is a Marketing Channel Manager at Mayo Clinic Laboratories. She is the principle editor and writer of Insights and leads social media and direct marketing strategy. Kelley has worked at Mayo Clinic since 2013. Outside of work, you can find Kelley running, traveling, playing with her kitty, and exploring new foods.