Intellectual developmental disorder — formative SAQs

SAQ 1 — Criteria, GDD and first-line evaluation (10 marks)

A 3-year-old is referred with delayed speech, delayed toilet training and inability to follow two-step commands. Hearing has not been formally assessed. There is no regression. The registrar asks whether this is “mild intellectual disability” and whether genetic testing can wait until school age. ^{[1] [5]}

Questions

1. Define intellectual developmental disorder using the three required elements, and explain why adaptive functioning is essential. (3 marks) ^[5]
2. Why is global developmental delay the better working label at age 3, and what actions must still happen now? (3 marks) ^[1]
3. Outline first-line aetiological and sensory evaluation priorities, including the role of chromosomal microarray. (4 marks) ^{[1] [2]}

Model answers

1. IDD requires significant deficits in intellectual functioning, significant deficits in adaptive functioning (conceptual, social, practical), and onset in the developmental period. Adaptive assessment is essential because intellectual scores and adaptive behaviour are related but not interchangeable; disability is defined by real-world function, not a lone IQ number. ^[5]
2. At age 3, formal cognitive testing is often unstable or invalid, so multi-domain delay is framed as GDD. You still open early intervention and education supports, complete hearing/vision pathways, take a full aetiological history/exam, and plan reassessment — you do not wait passively for school entry. ^[1]
3. Priorities: hearing and vision; chromosomal microarray as first-tier genetic testing for developmental disabilities; fragile X when indicated; phenotype-driven metabolic tests if red flags; consider broader sequencing later per ACMG CA/ID guidance and local access. Supports run in parallel with testing. ^{[2] [3] [10]}