A nationwide prospective randomized trial for diagnosing developmental disorders demonstrates genome sequencing outperforms standard of care.

Abstract

Backgroundexome (ES) or genome (GS) sequencing are recommended as first- or second-tier molecular tests for patients with developmental disorders (DD), but the clinical utility of GS continues to be debated. MethodsThis prospective randomized trial involving all Belgian Human Genetics centers compared the standard of care (SoC) - combining ES and chromosomal microarray analysis or shallow GS - with GS for 567 individuals with unexplained DD. ResultsThe diagnostic yield of GS was 39.8% (113/284) vs 30% for SoC (85/283) (p=0.015), mainly due to an increased detection of single nucleotide variants and indels (+8.7%). GS also enabled the detection of three non-coding (potential) pathogenic variants. Diagnostic yield was higher for females (45.5%, 97/213) compared to males (28.5%, 101/354) (p<0.001). De novo variants were found for 23.6% of patients. Analysis of inherited variants in genes associated with autosomal dominant phenotypes contributed more to the diagnostic yield (3.9%) than X-linked variants (1.9%), and to a similar extent as autosomal recessive variants (4.1%). ConclusionThis nationwide study indicates GS outperforms SoC for the diagnosis of patients with DD in a decentralized hospital setting and well-characterized cohort. The results also highlight the importance of evaluating autosomal dominant inherited variants in genomics analyses for DD.