title: The psychometric properties of the Quantitative-Checklist for Autism in Toddlers (Q-CHAT) as a measure of autistic traits in a community sample of Singaporean infants and toddlers.
abstract: BACKGROUND
  There is growing research evidence that subclinical autistic traits are elevated in relatives of individuals with autism spectrum disorder (ASD), continuously distributed in the general population and likely to share common etiology with ASD. A number of measures have been developed to assess autistic traits quantitatively in unselected samples. So far, the Quantitative-Checklist for Autism in Toddlers (Q-CHAT) is one of very few measures developed for use with toddlers as young as 18 months, but little is known about its measurement properties and factor structure.
  
  
  METHODS
  The present study examined internal consistency, factor structure, test-retest stability, and convergent validity of the Q-CHAT in a sample of toddlers in Singapore whose caregivers completed the Q-CHAT at 18 (n = 368) and 24 months (n = 396).
  
  
  RESULTS
  Three factors were derived accounting for 38.1 % of the variance: social/communication traits, non-social/behavioral traits, and a speech/language factor. Internal consistency was suboptimal for the total and speech/language scores, but acceptable for the social/communication and non-social/behavioral factor scores. Scores were generally stable between 18 and 24 months. Convergent validity was found with the Pervasive Developmental Disorders subscale of the Child Behavior Checklist (CBCL) completed by caregivers when their children were 24 months. Q-CHAT total scores in this sample were higher than those reported in other unselected samples from the UK.
  
  
  CONCLUSIONS
  The Q-CHAT was found to have a three-factor structure, acceptable internal consistency for its two main factor scores (social/communication and non-social/behavioral), normally distributed scores in an unselected sample, and similar structure and measurement properties as those reported in other published studies. Findings are discussed in relation to existing literature and future directions for the validation of the Q-CHAT.
authors.affiliation: Department of Psychology, National University of Singapore, #02-24, Block AS4, 9 Arts Link, 117570 Singapore, Singapore.
authors.forename: I
authors.initials: I
authors.lastname: Magiati
authors.affiliation: Department of Psychology, National University of Singapore, #02-24, Block AS4, 9 Arts Link, 117570 Singapore, Singapore.
authors.forename: D A
authors.initials: DA
authors.lastname: Goh
authors.affiliation: Department of Psychology, National University of Singapore, #02-24, Block AS4, 9 Arts Link, 117570 Singapore, Singapore.
authors.forename: S J
authors.initials: SJ
authors.lastname: Lim
authors.affiliation: Department of Psychology, National University of Singapore, #02-24, Block AS4, 9 Arts Link, 117570 Singapore, Singapore.
authors.forename: D Z Q
authors.initials: DZ
authors.lastname: Gan
authors.affiliation: Department of Psychology, National University of Singapore, #02-24, Block AS4, 9 Arts Link, 117570 Singapore, Singapore.
authors.forename: J C L
authors.initials: JC
authors.lastname: Leong
authors.affiliation: Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, UK.
authors.forename: C
authors.initials: C
authors.lastname: Allison
authors.affiliation: Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, UK.
authors.forename: S
authors.initials: S
authors.lastname: Baron-Cohen
authors.affiliation: Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research (A STAR), Singapore, Singapore.
authors.forename: A
authors.initials: A
authors.lastname: Rifkin-Graboi
authors.affiliation: Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research (A STAR), Singapore, Singapore ; Department of Psychological Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore.
authors.forename: B F P
authors.initials: BF
authors.lastname: Broekman
authors.affiliation: Saw Swee Hock School of Public Health, National University of Singapore, National University Health System, Singapore, Singapore.
authors.forename: S-M
authors.initials: SM
authors.lastname: Saw
authors.affiliation: Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research (A STAR), Singapore, Singapore ; Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore.
authors.forename: Y-S
authors.initials: YS
authors.lastname: Chong
authors.affiliation: Department of Maternal Fetal Medicine, KK Women's and Children's Hospital, Singapore, Singapore.
authors.forename: K
authors.initials: K
authors.lastname: Kwek
authors.affiliation: Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research (A STAR), Singapore, Singapore ; Liggins Institute, University of Auckland, Auckland, New Zealand.
authors.forename: P D
authors.initials: PD
authors.lastname: Gluckman
authors.affiliation: Department of Child Development, KK Women's and Children's Hospital, Singapore, Singapore.
authors.forename: S B
authors.initials: SB
authors.lastname: Lim
authors.affiliation: Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research (A STAR), Singapore, Singapore ; Ludmer Centre for Neuroinformatics and Mental Health, McGill University, Verdun, Canada; Department of Psychiatry, Faculty of Medicine, McGill University, Montreal, Canada.
authors.forename: M J
authors.initials: MJ
authors.lastname: Meaney
keywords: Assessment; Autism spectrum disorder; Autistic traits; Checklist; Dimensional; Factor structure; Measure; Psychometric properties; Quantitative; Toddlers