PSYCHOLOGICAL MARKERS IN THE DETECTION OF AUTISM IN INFANCY IN A LARGE POPULATION

Background. Investigation to see if there are key psychological risk i ndicators for autism in a random population study of children at 18 mo nths of age; and to assess how well these discriminate children who re ceive a diagnosis of autism from other forms of developmental delay. M ethod. Sixteen thousand children in the southeast of England were scre ened for autism by their health visitor or GP, during their routine 18 -month-old developmental check-up, using the CHAT (Checklist for Autis m in Toddlers). From a previous high-risk study we predicted that chil dren at 18 months of age who failed three items ('protodeclarative poi nting', 'gaze-monitoring', and 'pretend play') would be at risk for re ceiving a diagnosis of autism. From other evidence, we further predict ed that those 18-month-olds who failed one or two of the key items (ei ther pretend play, or protodeclarative pointing and pretend play) woul d be at risk for developmental delay without autism. Results: Twelve c hildren out of the total population of 16 000 consistently failed the three key items. Of these, 20 (83.3%) received a diagnosis of autism. Thus, the false positive rate was 16.6% (2 out of 12 cases), and even these 2 cases were not normal. When the 10 children with autism were r eassessed at 3.5 years of age, their diagnosis remained the same. Thus the false positive rate among the cases diagnosed with autism was zer o. In contrast, of 22 children who consistently failed either protodec larative pointing and/or pretend play, none received a diagnosis of au tism but 15 (68.2%) received a diagnosis of language delay. Conclusion s. Consistent failure of the three key items from the CHAT at 18 month s of age carries an 83.3% risk of autism; and this pattern of risk ind icator is specific to autism when compared to other forms of developme ntal delay.