Authors: Colin Reilly, Audrey Campbell & Patricia Keran

Keywords: Autism Spectrum Disorders • Early Diagnosis ASDs

Introduction
The purpose of this article is to review a number of instruments used in screening for ASDs in children under three years of age, and to discuss some of the issues involved in screening these children. The term “autism” will be used interchangeably with “Autistic Disorder”, as much of the reviewed literature refers to “Autistic Disorder” simply as “autism”.

There is a considerable history in the literature on studies examining instruments and issues related to screening for Autistic Disorder. There have been fewer studies specifically focused on other ASDs, although the term ASD has been used in much of the recent research on screening instruments, and thus can be presumed to include all the ASDs mentioned in the DSM–IV–TR. Autistic Disorder and PDD–NOS are much more likely to be diagnosed in the preschool period than Asperger’s Disorder, which is more likely to be diagnosed during school age or even later (Howlin & Moore, 1997). The majority of cases of Rett’s Disorder – which only affects females – have an identifiable genetic cause, while Childhood Disintegrative Disorder is a rare condition characterised by a very marked loss of skills.

Early Diagnosis of ASDs
The early identification of ASDs may increase the success rate of interventions (Greenspan, 1992; Lovaas, 1987) and may also allow time for genetic counseling and to initiate parental support (Baird et al., 2001). The early identification of ASDs is not without challenges. ASDs are behaviourally based diagnoses, and there is often a lack of familiarity with behavioural manifestations among front-line health and educational professionals. Some of the behaviours specified by the DSM–IV–TR (APA, 2000) for the diagnosis of ASDs in older children may not be present in young children with ASDs because they have not developed the prerequisite skills to exhibit the behaviour (Stone et al., 1999) and this has led to calls for more developmentally sensitive criteria (Chawarska & Volkmar, 2005). A difficulty with screening children for ASDs at a very young age is that there is no “gold standard” that allows immediate confirmation that a child in the second year of life with a score in the at risk range on a screening instrument is on the trajectory for developing an ASD (Watson et al., 2007).