This document provides information about microarray-based comparative genomic hybridisation (array CGH) testing. It discusses: - What array CGH is and how it works to detect smaller chromosome imbalances than traditional testing methods. - The potential benefits of an array CGH diagnosis, such as guiding monitoring and management of health issues, eligibility for support services, and relief of no longer needing multiple tests. - Limitations, including that many genes' functions are unknown, so the implications of imbalances are unclear. A diagnosis may not change treatment but provides closure.