Screening for autism in infants and toddlers

by Jon Brock in Cracking the Enigma

It’s widely believed that early intervention is crucial for long-term prognosis in autism and that the earlier the intervention begins the better. Getting in early, of course, requires that autistic children are identified at a young age. But even for more severe forms of autism, children are rarely diagnosed before three to four years of age. With this in mind, the American Academy of Pediatrics has recommended screening all toddlers for autism.However, writing in next July’s issue of Pediatrics (the academy’s own journal), Mona Al Qabandi and colleagues argue against routine population-based screening for autism. Chief amongst their objections is that existing screening tools are simply not up to the task. Most of these screens involve a questionnaire given to parents, sometimes augmented with a brief phone interview. But they all have their problems. Some are insensitive, missing a large number of kids who go on to get an ASD diagnosis further down the line. Others are sensitive but not specific, hoovering up all kinds of kids, many of whom don’t have autism, and may not have any kind of developmental problems at all.Al Qabandi et al. conclude that “none of the autism screening tests currently available has been shown to be able to fulfill the properties of accuracy… in a population-wide screening program”.Similar conclusions were reached in an earlier review by Josephine Barbaro and Cheryl Dissanayake at the Olga Tennison Autism Research Centre in Melbourne. So they tried a different approach. Rather than relying on parental questionnaires, they set up a 'surveillance program', training community nurses to spot the signs of autism during regular infant health checks.Each nurse attended a short two-and-a-half-hour workshop in which they were shown how to complete the screen. They were given a checklist with key behaviours to monitor, depending on the child’s age, and were trained how to score each item as either typical, atypical, or absent. For instance, the item for “eye contact” read as follows:"Has the child spontaneously made eye contact with you during the session? If not, interact with the child to elicit eye contact. Does s/he make eye contact with you?"From an initial sample of almost 21 thousand children, 216 were identified as “at risk” of ASD by 24 months of age. Of these, 110 completed further assessment, including the ADOS and ADI-R. 89 of these kids received an ASD diagnosis, giving the surveillance program a positive predictive value of 81%. Of the remaining 21 children, all but one had developmental language disorders.Calculating the screening program’s sensitivity is an inexact process at this stage. But assuming that the rates were similar for the children who did not undergo further assessment, Barbaro and Dissanayake estimated that approximately 175 ASD children would have been picked up. Dividing this by the total number of kids in the program gave an estimated prevalence of 1 in 119. This is reassuringly close to recent estimates of approximately 1 in 100 kids having an ASD, suggesting that the screen managed to pick up the majority of ASD kids in the initial sample.To get a more accurate indication of sensitivity, however, the researchers will have to wait until the children enter school. Only then will they be able to work out how many children end up with an ASD diagnosis but weren’t picked up by the screening measure.While it’s still early days, the Melbourne study suggests that population-wide screening for autism is possible, at least in areas that already have comprehensive child health checks. References:Barbaro, J., & Dissanayake, C. (2010). Prospective Identification of Autism Spectrum Disorders in Infancy and Toddlerhood Using Developmental Surveillance: The Social Attention and Communication Study Journal of Developmental & Behavioral Pediatrics, 31 (5), 376-385 DOI: 10.1097/DBP.0b013e3181df7f3cAl-Qabandi M, Gorter JW, & Rosenbaum P (2011). Early Autism Detection: Are We Ready for Routine Screening? Pediatrics PMID: 21669896Links:Olga Tennison Autism Research CentreFurther reading:Irresponsible Pediatrics article argues against autism screeningNot ready for introduction of routine screening for autism? Clarifying the issuesThe case against caution... Read more »