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Array CGH as a first line diagnostic test in place of karyotyping for postnatal referrals - results from four years’ clinical application for over 8,700 patients

Joo Wook Ahn1*, Susan Bint2, Anne Bergbaum2, Kathy Mann2, Richard P Hall2 and Caroline Mackie Ogilvie1

Author Affiliations

1 Cytogenetics Department, Guy’s and St Thomas’ NHS Foundation Trust, London, SE1 9RT, UK

2 Cytogenetics Department, GSTS Pathology, London, SE1 9RT, UK

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Molecular Cytogenetics 2013, 6:16  doi:10.1186/1755-8166-6-16

Published: 5 April 2013



Array CGH is widely used in cytogenetics centres for postnatal constitutional genome analysis, and is now recommended as a first line test in place of G-banded chromosome analysis. At our centre, first line testing by oligonucleotide array CGH for all constitutional referrals for genome imbalance has been in place since June 2008, using a patient vs patient hybridisation strategy to minimise costs.


Out of a total of 13,412 patients tested with array CGH, 8,794 (66%) had array CGH as the first line test. Referral indications for this first line group ranged from neonatal congenital anomalies through to adult neurodisabilities; 25% of these patients had CNVs either in known pathogenic regions or in other regions where imbalances have not been reported in the normal population. Of these CNVs, 46% were deletions or nullisomy, 53% were duplications or triplications, and mosaic imbalances made up the remainder; 87% were <5Mb and would likely not be detected by G-banded chromosome analysis. For cases with completed inheritance studies, 20% of imbalances were de novo.


Array CGH is a robust and cost-effective alternative to traditional cytogenetic methodology; it provides a higher diagnostic detection rate than G-banded chromosome analysis, and adds to the sum of information and understanding of the role of genomic imbalance in disease. Use of novel hybridisation strategies can reduce costs, allowing more widespread testing.

Array CGH; First line testing; G-banded karyotype analysis; CNV