Utility of second-generation sequencing and third-generation sequencing in the diagnosis of patients with intellectual disability: Rapid review

Introduction: Some populations have an intellectual disability frequency of nearly 18%. Among, the diverse genetic causes are single nucleotide variants and copy number variations, detected with second-generation sequencing and chromosomal microarray analysis, respectively. Nevertheless, other variants such as structural variants, trinucleotide repeat or imprinting disorders, cannot be detected by these tests and require different specific techniques. Third-generation sequencing have a power of found all variants. The purpose is to stablish the benefits of using third generation sequencing above second-generation sequencing in the diagnosis of patient with intellectual disability. Material and methods: A rapid systematic review was performed on the Medline using thesaurus terms MESH of “intellectual disability” and “second-generation sequencing”; as well as using the term “third-generation sequencing”. Results: 31 articles were selected in total. Of those, nine used third-generation sequencing in patients with previously genomic test, and founded structural variants in 40% of cases, all these variants were corroborated with other gold standard tests. Twenty-two studies used second-generation sequencing (n = 22) and showed through metanalysis, that 29,8% and 9,2% of these cases are due a single nucleotide variant and copy number variations, respectively. Conclusions: Third-generation sequencing can find structural variants, uniparental disomies, trinucleotide repeat and single nucleotide variation. Therefore, it would allow a broader and better study of the etiology of intellectual disability. Nevertheless, more research with larger representative samples in patients and healthy population is needed.