Key messages
- Nine out of 10 preschool aged children diagnosed with autism in a research setting may continue to meet diagnostic criteria one or more years later.
- Due to lack of robust evidence, this finding may not be able to be generalised to children outside a research setting, and we were not able to identify any child or research study factors that influenced if a child retained their diagnosis.
- Future research should focus on designing a robust study exploring whether a child retains their autism diagnosis over time in clinical practice and what other factors, if any, may change how likely a child is to retain their diagnosis.
What is autism?
Autism (autism spectrum disorder) is a common neurodevelopmental condition that is generally considered to be lifelong. It is characterised by difficulties in social communication, and restricted interests and repetitive behaviours. How much of a challenge these areas present for each individual is highly variable.
How is autism diagnosed?
Autism is diagnosed by assessing whether an individual meets a set of standardised diagnostic criteria.
In children, an autism diagnostic assessment may involve a paediatrician, child psychiatrist, speech pathologist, occupational therapist and psychologist. One or more of these health professionals may observe and ask questions about a child’s social and communication skills, any difficulties in restricted interests and repetitive behaviours, and how they process and respond to sensory information from the world around them. There are diagnostic assessment tools that these professionals can use, alone or in combination, to help make the diagnosis.
What is diagnostic stability, and why is it important?
Diagnostic stability refers to whether an individual retains their diagnosis over time. The diagnostic stability of autism is important to help health professionals, autistic individuals and their families understand how likely it is for a diagnosis of autism spectrum disorder to be lifelong. Additionally, it helps government and community groups to plan what health, education and employment resources are required to support autistic children and their families. Diagnostic stability also helps us to understand whether the characteristics of autistic children and the way that autism spectrum disorder is currently diagnosed influences whether a child continues to meet the criteria for an autism diagnosis over time.
What did we want to find out?
We wanted to find out whether a preschool child who was given a diagnosis of autism spectrum disorder before the age of six years retained their diagnosis at repeat diagnostic assessment one or more years later.
We also wanted to learn more about whether any factors relating to the individual child, the way the child was diagnosed with autism, or the research methods used in the studies, made it more or less likely for the child to continue to meet diagnostic criteria for autism spectrum disorder over time. The factors relating to the individual child included the children's age at the initial and follow-up diagnostic assessments, their intelligence quotient (IQ) score, their ability to complete daily living tasks for a child of their age (adaptive behaviour score), and their ability to communicate with those around them (language score). Factors relating to the way children were diagnosed included the type of tool or criteria used to make the diagnosis, the length of time between diagnostic assessments, and whether the diagnosis was made by a multidisciplinary team. The factors related to the research methods included the year the study was published and the robustness of the evidence.
What did we do?
We searched for studies looking at preschool aged children diagnosed with autism. We then summarised the results, evaluated the evidence and rated our confidence in the evidence based on factors such as study methods and participation.
What did we find?
In total, 49 studies met our inclusion criteria and 42 of these (11,740 children) had data that could be used. The biggest study had 8564 children and the smallest had 11. These studies were from 13 countries, with 16 from the USA. The average age of the children was three years at their first diagnosis and six years at follow-up. The average length of follow-up was 2.86 years.
We found that, in a research setting, nine out of 10 of preschool children diagnosed with autism spectrum disorder may keep their diagnosis one or more years later.
What are the limitations of the evidence?
We have little confidence in the evidence because not all the studies provided data about everything that we were interested in, and the studies were done with different types of people and diagnostic assessments.
For the one in 10 children who no longer met diagnostic criteria for an autism diagnosis at follow-up, we were not able to tell whether they had 'grown out' of their autism because they became more mature over time, or because they had received intervention, or whether the original diagnosis was inaccurate.
How up to date is this evidence?
The evidence is up to date to July 2021.
Overall, we found that nine out of 10 children who were diagnosed with autism spectrum disorder before six years of age continued to meet diagnostic criteria for autism spectrum disorder a year or more later, however the evidence was uncertain. Confidence in the evidence was rated low using GRADE, due to heterogeneity and risk of bias, and there were few studies that included children diagnosed using a current classification system, such as the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) or the eleventh revision of the International Classification of Diseases (ICD-11). Future studies that are well-designed, prospective and specifically assess prognosis of autism spectrum disorder diagnoses are needed. These studies should also include contemporary diagnostic assessment methods across a broad range of participants and investigate a range of relevant prognostic factors.
Autism spectrum disorder is a neurodevelopmental disorder characterised by social communication difficulties, restricted interests and repetitive behaviours. The clinical pathway for children with a diagnosis of autism spectrum disorder is varied, and current research suggests some children may not continue to meet diagnostic criteria over time.
The primary objective of this review was to synthesise the available evidence on the proportion of preschool children who have a diagnosis of autism spectrum disorder at baseline (diagnosed before six years of age) who continue to meet diagnostic criteria at follow-up one or more years later (up to 19 years of age).
We searched MEDLINE, Embase, PsycINFO, and eight other databases in October 2017 and ran top-up searches up to July 2021. We also searched reference lists of relevant systematic reviews.
Two review authors independently assessed prospective and retrospective follow-up studies that used the same measure and process within studies to diagnose autism spectrum disorder at baseline and follow-up. Studies were required to have at least one year of follow-up and contain at least 10 participants. Participants were all aged less than six years at baseline assessment and followed up before 19 years of age.
We extracted data on study characteristics and the proportion of children diagnosed with autism spectrum disorder at baseline and follow-up. We also collected information on change in scores on measures that assess the dimensions of autism spectrum disorder (i.e. social communication and restricted interests and repetitive behaviours). Two review authors independently extracted data on study characteristics and assessed risk of bias using a modified quality in prognosis studies (QUIPS) tool. We conducted a random-effects meta-analysis or narrative synthesis, depending on the type of data available. We also conducted prognostic factor analyses to explore factors that may predict diagnostic outcome.
In total, 49 studies met our inclusion criteria and 42 of these (11,740 participants) had data that could be extracted. Of the 42 studies, 25 (60%) were conducted in North America, 13 (31%) were conducted in Europe and the UK, and four (10%) in Asia. Most (52%) studies were published before 2014. The mean age of the participants was 3.19 years (range 1.13 to 5.0 years) at baseline and 6.12 years (range 3.0 to 12.14 years) at follow-up. The mean length of follow-up was 2.86 years (range 1.0 to 12.41 years). The majority of the children were boys (81%), and just over half (60%) of the studies primarily included participants with intellectual disability (intelligence quotient < 70). The mean sample size was 272 (range 10 to 8564). Sixty-nine per cent of studies used one diagnostic assessment tool, 24% used two tools and 7% used three or more tools. Diagnosis was decided by a multidisciplinary team in 41% of studies. No data were available for the outcomes of social communication and restricted and repetitive behaviours and interests.
Of the 42 studies with available data, we were able to synthesise data from 34 studies (69% of all included studies; n = 11,129) in a meta-analysis. In summary, 92% (95% confidence interval 89% to 95%) of participants continued to meet diagnostic criteria for autism spectrum disorder from baseline to follow-up one or more years later; however, the quality of the evidence was judged as low due to study limitations and inconsistency. The majority of the included studies (95%) were rated at high risk of bias. We were unable to explore the outcomes of change in social communication and restricted and repetitive behaviour and interests between baseline and follow-up as none of the included studies provided separate domain scores at baseline and follow-up. Details on conflict of interest were reported in 24 studies. Funding support was reported by 30 studies, 12 studies omitted details on funding sources and two studies reported no funding support. Declared funding sources were categorised as government, university or non-government organisation or charity groups. We considered it unlikely funding sources would have significantly influenced the outcomes, given the nature of prognosis studies.