Lay summary
Chromosomal microarray analysis is a basic first-line clinical investigation for children with neurodevelopmental delay. The platforms used for these tests exploit sites across the genome that are known to be variable to detect chromosomal imbalance. It is a well recognised observation that CMA analysis on tamariki often yields results that indicate that either the parents of these children have shared ancestry (an observation that would be important for subsequent genetic analyses) or that the platform is not optimally configured to assess for genetic disorders in these children (representing a serious issue of equity). We propose to survey CMA results nationally using a retrospective approach to measure and address these possibilities, and then adopt a prospective approach to see if a more optimal approach will enhance diagnostic yields for whānau.