There are few epidemiological studies and limited knowledge of ASC in mainland China. Modern screening and standardised diagnostic instruments have not been adopted in mainland China, which makes comparison of the prevalence of Autism Spectrum Conditions (ASC) in the East and West difficult.
1. To test the utility of a screening instrument for ASC, a Mandarin Chinese version of the Childhood Autism Spectrum Test (CAST); 2. To apply standardised diagnostic instruments to a Chinese population for diagnosis confirmation for the first time; 3. To establish a prevalence estimate of ASC in an undiagnosed population in mainland China; 4. To validate the existing diagnosis of ASC in mainland China.
We followed the design used previously in the UK (British J. Psychiatry, 2009). The Mandarin CAST was validated through screening two primary school pupils (N = 737 children age 6-10 years old) in Beijing and by conducting diagnostic assessments with a proportion of the screened children using the ADOS and ADI-R. The prevalence estimate was generated using the inverse probability weighting. The number of undiagnosed children in mainstream schools was calculated after adjusting and imputing for missing values (including age, sex and non response effects). The test-retest reliability of the Mandarin CAST was examined in the assessment sample of the validation (N=103) using Cohen’s Kappa, and the exploration of the psychometric properties was conducted in the validation sample using categorical data factor analysis (CDFA) and the item response theory (IRT). N = 50 cases with an existing diagnosis of autism were also re-examined using the ADOS and ADI-R.
Response was high (97%). Using the UK cut-off (≥15), CAST performance was 84% sensitivity and 96% specificity (95% CI 46, 98 and 96, 97 respectively). 6/103 children, not previously diagnosed, were found to meet diagnostic criteria (8.5 after adjustment, 95% CI: 1.6, 15.4). The preliminary prevalence in an undiagnosed primary school population in mainland China was 119 per 10,000 (95% CI: 53, 265). Of 50 children with an existing diagnosis of autism by Chinese clinicians, 47 children met the diagnosis of autism on the ADOS and 44 children met the diagnosis of autism on the ADI-R. Using a cut-off score of 15, the test-retest reliability was good (Kappa=0.64). The test-retest reliability in three categories (≤11, 12-14, ≥15) was moderate (Weighted Kappa=0.53). The exploratory factor analysis proposed a two-factor solution for the Mandarin CAST which comprised Social and Communication, and Inflexible/Stereotyped Language and Behaviours.
The utility of CAST is acceptable as a screening instrument for ASC in large epidemiological studies in China. There are undiagnosed children on the autism spectrum in primary schools in the general population in China. Using a comparable method, the preliminary prevalence estimate of ASC in mainland China is similar to that of Western estimates. Because this was only based on 2 schools (n = 737 children), a larger-scale prevalence study is now underway to confirm this preliminary estimate, in 14 regions across China with the aim of screening n = 20,000 children per region.
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