Screening for Autism and Intellectual Disabilities amongst the Nigerian Adolescent Population

Autism and intellectual disabilities awareness is increasing globally, perhaps due to the availability of technology and global migration. The ability to detect these disabilities in the West continues to grow as new screening tools are developed and previous screening and diagnostic methods are revised. This is not the case in Africa and Nigeria specifically. The inability to use standardised measures in assessing for these disabilities poses a challenge and impedes the ability to provide intervention for the affected population. While there are readily available tools online for screening autism in early years, there is no evidence of their cross-cultural validation in most African countries and Nigeria especially. There is also limited evidence for the availability and validation of screening tools for adolescents globally. Therefore, persons who are suspected to have autism in later years are not properly assessed. Regarding intellectual disability, there is no screening tool readily available for adolescents. Diagnosing intellectual disability requires a multi-tiered approach but starts with screening. Assessing adolescents with intellectual disability in Africa is also a challenge as there is limited access to measures by professionals. There are very few screening tools available for intellectual disability and even more limited for adolescents.

This thesis sought to identify screening tools for both intellectual disability and autism, that may be culturally appropriate for use within Africa. Where there are non-readily available, the thesis explored the possibility of adapting existing tools for autism and intellectual disability. The focus on both disabilities is due to their often comorbidity.

Study 1 was a systematic review which identified, described, and critically appraised short screening tools for the detection of intellectual disabilities and autism for older children and young adults. The psychometric properties of these tools were then examined for their cultural appropriateness for use within Africa. Six screening tools for intellectual disabilities and twelve for autism were identified and appraised using the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) guidelines. Two screening tools each for autism and intellectual disability appeared appropriate for validation for use within African nations.

Study 2 was a focus group meeting which employed the Nominal Group Technique (NGT). The group examined the identified screening tools for the items' face and content validity and cultural relevance. The group consisted of professionals, parents, and laypersons who selected two of the four existing screening tools for autism spectrum disorder and intellectual disability for adaptation and use with older children and adolescents in Nigeria.

Study 3a involved the validation of the selected tool for intellectual disability, the English version of the adolescent Screener for Intelligence and Learning Disabilities (SCIL). The psychometric properties of the tool when used with Nigerian adolescents were assessed. There were two hundred and nine adolescents and young people (aged 11 - 26 years) who completed the SCIL and took part in an assessment of their level of general intellectual functioning and adaptive behaviour. The study determined that the SCIL has good psychometric properties when used with Nigerian adolescents.

Study 3b was the validation of the selected tool for autism, the Social Communication Questionnaire (SCQ). The psychometric properties of the tool when used with Nigerian adolescents were assessed. Parents and caregivers of two hundred and five adolescents completed the SCQ Lifetime form while the adolescents were assessed for autism using the Autism Diagnostic Observation Schedule, 2nd Edition (ADOS-2). Convergent and discriminant validity were examined, along with the sensitivity and specificity of the SCQ in identifying participants with an autism spectrum disorder. The SCQ has good psychometric properties when used with Nigerian adolescents.