Intellectual Disability (IDNext)

2-3% of Americans are diagnosed with intellectual disability (ID).1 Genetic testing is recommended for all children with ID and can identify the underlying cause for about 1 in every 5 affected individuals.2 Distinguishing the underlying molecular cause can be critical to accurate diagnosis, treatment, prognosis, and genetic counseling.

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Test Code 7027
Turnaround Time (TAT) 5-7 weeks
Number of Genes 140
Specimen Requirements Click here

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Mutation Detection Rate

IDNext can detect >99.9% of described mutations in the included genes, when present (analytic sensitivity).

Test Description

Our IDNext panel includes 140 genes associated with intellectual disability. This test includes gene sequencing and deletion/duplication analysis. FMR1 repeat expansion testing and Angelman/Prader-Willi methylation studies are not included in this test, but can be ordered concurrently. Genomic deoxyribonucleic acid (gDNA) is isolated from the patient’s specimen using a standardized kit and quantified. Sequence enrichment of the targeted coding exons and adjacent intronic nucleotides is carried out by a bait-capture methodology using long biotinylated oligonucleotide probes, followed by polymerase chain reaction (PCR) and next generation sequencing (NGS). 

Sanger sequencing is performed for any regions missing, or with insufficient read depth coverage for reliable heterozygous variant detection. Reportable small insertions and deletions, potentially homozygous variants, variants in regions complicated by pseudogene interference, and single nucleotide variant calls not satisfying 100x depth of coverage and 40% het ratio thresholds are verified by Sanger sequencing. This assay targets all coding domains, and well into the flanking 5’ and 3’ ends of all the introns and untranslated regions. Gross deletion/duplication analysis for available genes is performed utilizing a targeted chromosomal microarray. 

1. Larson SL, et al. Prevalence of mental retardation and/or developmental disabilities: Analysis of the 1994/1995 NHIS-D. MR/DD Data Brief. Minneapolis, MN: Institute on Community Integration, University of Minnesota. 2000.

2. Miller DT, 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 May 14;86(5):749-764.

3. Mu W, et al. Sanger confirmation is required to achieve optimal sensitivity and specificity in next-generation sequencing panel testing. J Mol Diagn. 2016. 18(6):923-932.

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