Open Access Research article

Detection of pathogenic copy number variants in children with idiopathic intellectual disability using 500 K SNP array genomic hybridization

JM Friedman12*, Shelin Adam1, Laura Arbour13, Linlea Armstrong14, Agnes Baross5, Patricia Birch1, Cornelius Boerkoel124, Susanna Chan5, David Chai14, Allen D Delaney5, Stephane Flibotte5, William T Gibson124, Sylvie Langlois14, Emmanuelle Lemyre6, H Irene Li5, Patrick MacLeod3, Joan Mathers4, Jacques L Michaud7, Barbara C McGillivray14, Millan S Patel14, Hong Qian5, Guy A Rouleau7, Margot I Van Allen14, Siu-Li Yong14, Farah R Zahir1, Patrice Eydoux4 and Marco A Marra15

Author Affiliations

1 Department of Medical Genetics, University of British Columbia, Vancouver, Canada

2 Child & Family Research Institute, Vancouver, British Columbia, Canada

3 Victoria General Hospital, Victoria, British Columbia, Canada

4 Children's & Women's Health Centre, Vancouver, British Columbia, Canada

5 Genome Sciences Centre, British Columbia Cancer Agency, Vancouver, Canada

6 CHU Sainte-Justine Research Center, Montréal, Québec, Canada

7 Center for Excellence in Neuromics of Université de Montréal, CHU Sainte-Justine Research Center, Montréal, Québec, Canada

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BMC Genomics 2009, 10:526  doi:10.1186/1471-2164-10-526

Published: 16 November 2009

Abstract

Background

Array genomic hybridization is being used clinically to detect pathogenic copy number variants in children with intellectual disability and other birth defects. However, there is no agreement regarding the kind of array, the distribution of probes across the genome, or the resolution that is most appropriate for clinical use.

Results

We performed 500 K Affymetrix GeneChip® array genomic hybridization in 100 idiopathic intellectual disability trios, each comprised of a child with intellectual disability of unknown cause and both unaffected parents. We found pathogenic genomic imbalance in 16 of these 100 individuals with idiopathic intellectual disability. In comparison, we had found pathogenic genomic imbalance in 11 of 100 children with idiopathic intellectual disability in a previous cohort who had been studied by 100 K GeneChip® array genomic hybridization. Among 54 intellectual disability trios selected from the previous cohort who were re-tested with 500 K GeneChip® array genomic hybridization, we identified all 10 previously-detected pathogenic genomic alterations and at least one additional pathogenic copy number variant that had not been detected with 100 K GeneChip® array genomic hybridization. Many benign copy number variants, including one that was de novo, were also detected with 500 K array genomic hybridization, but it was possible to distinguish the benign and pathogenic copy number variants with confidence in all but 3 (1.9%) of the 154 intellectual disability trios studied.

Conclusion

Affymetrix GeneChip® 500 K array genomic hybridization detected pathogenic genomic imbalance in 10 of 10 patients with idiopathic developmental disability in whom 100 K GeneChip® array genomic hybridization had found genomic imbalance, 1 of 44 patients in whom 100 K GeneChip® array genomic hybridization had found no abnormality, and 16 of 100 patients who had not previously been tested. Effective clinical interpretation of these studies requires considerable skill and experience.