High‐resolution molecular karyotyping in patients with developmental delay and/or multiple congenital anomalies in a clinical setting

Wincent J, Anderlid B‐M, Lagerberg M, Nordenskjöld M, Schoumans J. High‐resolution molecular karyotyping in patients with developmental delay and/or multiple congenital anomalies in a clinical setting. Microarray‐based comparative genomic hybridization (array‐CGH) enables genomewide investigation of copy‐number changes at high resolution and has recently been implemented as a clinical diagnostic tool. In this study we evaluate the usefulness of high‐resolution arrays as a diagnostic tool in our laboratory and investigate the diagnostic yield in the first 160 patients who were clinically referred for investigation of developmental delay (DD)/multiple congenital anomalies (MCA). During this period both 38K BAC‐arrays and 244K oligonucleotide‐arrays were used. Copy‐number variations (CNVs) not previously reported as normal variants were detected in 22.5% of cases. In 13.1% the aberrations were considered causal to the phenotype and in 9.4% the clinical significance was uncertain. There was no difference in diagnostic yield between patients with mild, moderate or severe DD. Although the effective resolution of the 244K oligonucleotide‐arrays was higher than the 38K BAC‐array, the diagnostic yield of both platforms was approximately equal and no causal aberrations <300 kb were detected in this patient cohort. We experienced that increasing the resolution of a whole genome screen in the diagnostic setting has its drawback of detecting an increased number of CNVs with uncertain contribution to a phenotype. Based on our experiences, array‐CGH is recommended as the first‐step analysis in the genetic evaluation of patients with DD and/or MCA.