Background. There is a recent trend of a worldwide increase in the incidence of autistic spectrum disorder. Early identification and intervention have proved to be beneficial. The original version of the Checklist for Autism in Toddlers ( CHAT) was a simple screening tool for identification of autistic children at 18 months of age in the United Kingdom. Children with an absence of joint attention (including protodeclarative pointing and gaze monitoring) and pretend play at 18 months were at high risk of autism. Section A of the CHAT was a self-administered questionnaire for parents, with 9 yes/no questions addressing the following areas of child development: rough and tumble play, social interest, motor development, social play, pretend play, protoimperative pointing ( pointing to ask for something), protodeclarative pointing, functional play, and showing. Section B of the CHAT consisted of 5 items, which were recorded with observation of the children by general practitioners or health visitors. The 5 items addressed the child's eye contact, ability to follow a point ( gaze monitoring), pretend ( pretend play), produce a point ( protodeclarative pointing), and make a tower of blocks. A 6-year follow-up study of >16 000 children screened with the CHAT at 18 months in the United Kingdom showed a sensitivity of only 0.40 and a specificity of 0.98, with a positive predictive value (PPV) of 0.26. Rescreening using the same instrument at 19 months for those who failed the 18-month screening yielded a higher PPV of 0.75. Therefore, children were likely to have autism if they failed the CHAT at 18 months and failed again at 19 months. It was estimated that consistent failure in 3 key questions (ie, protodeclarative pointing, gaze monitoring, and pretend play) at 18 months indicated an 83.3% risk of having autism. Because of the poor sensitivity of the original CHAT for autism, a Modified Checklist for Autism in Toddlers (MCHAT), consisting of 23 questions, with 9 questions from the original CHAT and an additional 14 questions addressing core symptoms present among young autistic children, was designed in the United States. The original observational part ( ie, section B) was omitted. The M-CHAT was designed as a simple, self-administered, parental questionnaire for use during regular pediatric visits. The more questions children failed, the higher their risk of having autism. Two criteria were used to measure the sensitivity and specificity of M-CHAT. Criterion 1 used any 3 of the 23 questions, and criterion 2 used 2 of the 6 best questions that could be used to discriminate autism from other groups. The sensitivity and specificity for criterion 1 were 0.97 and 0.95 and those for criterion 2 were 0.95 and 0.99, respectively. M-CHAT had a better sensitivity than the original CHAT, because children up to 24 months of age were screened, with the aim of identifying those who might regress between 18 and 24 months. The 6 best questions of the M-CHAT addressed areas of social relatedness ( interest in other children and imitation), joint attention (protodeclarative pointing and gaze monitoring), bringing objects to show parents, and responses to calling. Joint attention was addressed in the original CHAT, whereas the other areas were addressed only in the M-CHAT. To date, there has been no study of the application of either the original CHAT or the M-CHAT for Chinese populations. Objectives. CHAT-23 is a new checklist translated into Chinese, combining the M-CHAT ( 23 questions) with graded scores and section B (observational section) of the CHAT. We aimed to determine whether CHAT-23 could discriminate autism at mental ages of 18 to 24 months for Chinese children and to determine the best combination of questions to identify autism. Methods. A cross-sectional cohort study was performed with 212 children with mental ages of 18 to 24 months. The children were categorized into 2 groups, ie, group 1 (N = 87) (autistic disorder: N = 53; pervasive developmental disorder: N = 33) and group 2 (N = 125) (nonautistic). The checklist included self-administered questionnaires with 23 questions ( part A) and direct observations of 5 items by trained investigators ( part B). We performed discriminant function analysis to determine the key questions that could best discriminate autism from nonautism. The sensitivity and specificity of CHAT-23 were calculated. Results. We found that 7 key questions, addressing areas of joint attention, pretend play, social relatedness, and social referencing, were identified as discriminative for autism. For part A, failing any 2 of 7 key questions, ie, question 13 (does your child imitate you? [eg, you make a face; will your child imitate it?]), question 5 ( does your child ever pretend, for example, to talk on the phone or take care of dolls, or pretend other things?), question 7 ( does your child ever use his/her index finger to point, to indicate interest in something?), question 23 ( does your child look at your face to check your reaction when faced with something unfamiliar?), question 9 ( does your child ever bring objects over to you [ parent] to show you something?), question 15 ( if you point at a toy across the room, does your child look at it?), and question 2 ( does your child take an interest in other children?), yielded sensitivity of 0.931 and specificity of 0.768. Failing any 6 of all 23 questions produced sensitivity of 0.839 and specificity of 0.848. For part B, failing any 2 of 4 items produced sensitivity of 0.736, specificity of 0.912, and PPV of 0.853. The 4 observational items were as follows: item B1: during the appointment, has the child made eye contact with you? item B2: does the child look across to see what you are pointing at? item B3: does the child pretend to pour out tea, drink it, etc?; item B4: does the child point with his/her index finger at the light? Conclusion. We found that integrating the screening questions of the M-CHAT ( from the United States) and observational section B of the original CHAT ( from the United Kingdom) yielded high sensitivity and specificity in discriminating autism at 18 to 24 months of age for our Chinese cohort. This new screening instrument (CHAT23) is simple to administer. We found that a 2-stage screening program for autism can offer a cost-effective method for early detection of autism at 18 to 24 months. For CHAT-23, use of both the parental questionnaire and direct observation and use of the criterion of failing any 2 of 7 key questions yielded the highest sensitivity but a relatively lower specificity, whereas use of part B yielded the highest specificity but a lower sensitivity. We recommend identifying the possible positive cases with part A ( parental questionnaire) and then proceeding to part B (observation) with trained assessors. The proposed algorithm for screening for autism is as follows. 1) The parents or chief caretakers complete a 23-item questionnaire when their children are 18 to 24 months of age. 2) The parents mail, fax, or hand this 23-item questionnaire to the local child health agency. 3) Clerical staff members check for and score failure, with the criteria of failing any 2 of 7 key questions or failing any 6 of 23 questions; if either criterion is met, then the staff members highlight the medical records of the suspicious cases. 4) Trained child health care professionals observe the children who failed any 2 of 7 key questions or any 6 of 23 questions. These identified patients are observed for 5 minutes for part B of the CHAT-23. 5) Any child who fails any 2 of 4 items requires direct referral to a comprehensive autism evaluation team, for early diagnostic evaluation and early intervention. The high sensitivity and specificity of the criteria observed in our study suggested that CHAT-23 might be used to differentiate children with autism. Additional international collaboration with the use of the CHAT, M-CHAT, and CHAT-23 could provide more prospective epidemiologic data, to establish whether there is a genuine increase in the worldwide incidence of autism.
