Genetic profile and clinical application of chromosomal microarray in children with intellectual disability in Hong Kong.

INTRODUCTION: Chromosomal microarray (CMA) is recommended as a first-tier genetic investigation for intellectual disability (ID), developmental delay, or autism spectrum disorder due to its higher diagnostic yield with respect to conventional karyotyping. The aim of the present study was to investigate the genetic profile and diagnostic yield of CMA in children with moderate, severe and profound ID.

METHODS: A pilot cross-sectional study was performed by the Child Assessment Service and the Clinical Genetic Service in Hong Kong from July 2016 to June 2017. Children with unexplained ID were recruited for CMA testing by an expedited referral pathway. Children who were existing clients of the Clinical Genetic Service were also recruited.

RESULTS: Of 225 children included in this study, 68 (30.2%) had genetic diagnoses. Among the 138 children who underwent CMA testing, 53 (38%) children were referred to the Clinical Genetic Service by the expedited referral pathway. The respective diagnostic yields of CMA in moderate, severe, and profound ID were 8.7%, 17.6%, and 23.5% (P<0.05). Children with dysmorphic features demonstrated a much higher yield from CMA (45.8% vs 4.4%, P<0.05). CONCLUSTION. The overall diagnostic yield (11.6%) of CMA in this cohort is comparable with that of other international cohorts. This further supports the use of CMA as a first-tier genetic investigation for children with ID, developmental delay, or autism spectrum disorder, particularly for those with severe disease.