Overall prognosis of preschool autism spectrum disorder diagnoses

The Cochrane Collaboration. Published by John Wiley & Sons, Ltd. This is a protocol for a Cochrane Review (Prognosis). The objectives are as follows: The primary objective of this review is to synthesise the available evidence on the proportion of individuals who have a diagnosis of autism spectrum disorder at baseline and at follow-up one or more years later. The secondary objectives of this review are to: investigate whether there are differences in the proportions of individuals with autism spectrum disorder who maintain a diagnosis at follow-up dependent on use of the different classification systems (i.e. DSM or ICD criteria) and their revisions; and investigate the proportion of individuals with autism spectrum disorder who maintain diagnosis at follow-up in important subgroups of individuals, including those of different ages and those with different language levels (verbal/non-verbal; standard score ≤ 70 or > 70), IQs (≤ 70 or > 70), adaptive behaviour (standard score ≤ 70 or > 70), and different diagnostic subgroups (Asperger's syndrome/disorder, autistic disorder, childhood autism, PDD-NOS, atypical autism, PDD and autism spectrum disorder). We will investigate potential sources of heterogeneity that may impact outcomes such as differences in study participation, study design, length of follow-up, participant attrition and participant outcome measurement factors. We will use internationally recognised standards for systematic reviews to guide the review.