Importance of patient selection criteria in determining diagnostic copy number variations in patients with multiple congenital anomaly/mental retardation

Abstract

Abstract Background Etiology of developmental delay/intellectual disability is very heterogeneous. In recent years, genetic causes have been defined through the use of chromosomal microarray analysis as a first step genetic test. Results Samples from 30 patients with multiple congenital anomaly and/or mental retardation were analyzed with array comparative genomic hybridization in the context of this study. Before this analysis, karyotyping, subtelomeric fluorescence in situ hybridization and additionally fragment analysis for fragile X in males, had been routinely made all of which were reported to be normal. The purpose of our study was to determine the copy number variations as well as to investigate methods to increase diagnostic yield of array comparative genomic hybridization and forming a suitable flow chart decision pipeline for test indication especially for developing countries. Genomic changes were identified at a rate of about 27% in our series. Although this ratio is higher than the literature data, it could be due to the patient selection criteria. Conclusion Chromosomal microarray analysis is not easily utilized for all patients because of its high-cost. Thus, for increasing cost-effectiveness, it may be used step by step for defined targets. Along with discussing the patients with copy number variations relevant with the phenotype, we suggest a flow chart for selection of diagnostic test with the highest diagnostic rate and the lowest expenditure which is quite important for developing countries.

Keywords

• Chromosomal microarray
• Multiple congenital anomaly
• Mental retardation
• Loop hybridization
• Patient selection criteria