Investigating developmental delay in South Africa: A pragmatic approach

Global developmental delay and intellectual disability are common disorders in every population, with a prevalence of 1 - 5%. Although a specific cause is not always immediately identifiable, for many affected people the aetiology is genetic or the result of secondary insult to the developing brain. Investigating children with intellectual developmental disorders (IDD) may be a significant challenge, especially in resource-limited settings. Comprehensive clinical evaluation is the first step and frequently determines the direction of further investigations. Hearing and vision screening and thyroid function tests should be performed in most patients. Children with neurological findings should undergo brain imaging, and careful consideration should be given to potential metabolic disorders in all children with IDD, a number of whom are amenable to treatment. Most children in whom a specific direction is not suggested after history-taking and examination, should be tested for chromosomal abnormalities, ideally with chromosomal microarray, which has a diagnostic detection rate of 8 - 20% in IDD. Additional tests may be indicated in particular settings, including broad-based testing for single-gene disorders, such as next-generation sequencing gene panels or exome analysis. All genetic testing has the potential of finding variants of uncertain significance, particularly when there are limited population data, such as in Africa. Making a specific diagnosis in IDD is of benefit to patients, their families and society. Therefore, a rational approach to investigating this group of patients is essential to maximise the health benefit in a cost-effective way