Summary of Advances
In Autism Spectrum Disorder Research
Race influences parent report of concerns about symptoms of autism spectrum disorder
Donohue MR, Childs AW, Richards M, Robins DL. Autism.. 2017 Nov 1:1362361317722030. [Epub ahead of print] [PMID: 29100475]
The average age of diagnosis of ASD in the U.S. is 4 years old, but most parents first report concerns about behavior much earlier, during the first two years of the child’s life. Early ASD diagnosis is important because it facilitates earlier intervention that may help children make greater gains in their skills and functioning by school age. However, racial disparities exist for children receiving an ASD diagnosis; Black children are generally diagnosed later in life than White children. There have been few studies to examine the possible reasons for this difference in diagnosis.
Parent report of concerns may be an important factor in early diagnosis. Studies show that Black parents are more likely than White parents to report concerns about disruptive behaviors but are less likely than White parents to report concerns about autism symptoms, which raises the question of whether Black parents sometimes observe ASD symptoms but report them as behavioral problems. Additionally, research has suggested that Black children are twice as likely to receive a misdiagnosis from a clinician before receiving an ASD diagnosis. The goal of this study was to investigate the differences in which Black and White parents report concerns about their children’s behavior and development as related to ASD symptoms. The researchers aimed to determine if fewer reported concerns by Black parents about ASD symptoms might be a contributing factor to the age difference in ASD diagnoses among Black and White children.
The study included 174 children with ASD between 18 and 40 months old, and their parents. The children were screened for ASD or pervasive developmental disorder not otherwise specified (a developmental disorder that is related to ASD). Prior to screening the children, the researchers asked the parents to fill out a free-response questionnaire describing their child’s development. Parent concerns were categorized into two groups: ASD concerns (which included speech/communication, restricted and repetitive behavior, social deficits, and directly naming autism) and non-ASD concerns (which included motor difficulties, behavior/temperament, medical/regulatory, general development, feeding/eating, and disruptive behavior).
The researchers found that Black parents reported fewer ASD concerns than did White parents, but that Black and White parents were equally likely to report non-ASD concerns. Among parents who reported ASD concerns, White parents were far more likely than Black parents to report a social or restricted and repetitive behavior concern. However, there were no significant differences in the likelihood to report speech concerns or to specifically mention autism. Among those who reported non-ASD concerns, Black parents and White parents were equally likely to report disruptive behavior, contradicting previous research that suggested that Black parents are more likely to report disruptive behavior.
The results of this study indicate that Black parents are less likely to report concerns about social behavior and restricted and repetitive behavior, which could be one contributing factor to a missed or delayed diagnosis by a clinican. The researchers suggest that future studies should examine if a lack of reported concerns is related to access to information about ASD symptoms among Black parents. Improving parents’ knowledge of and ability to communicate about ASD symptoms may be an area that can be targeted to reduce the current disparities in age difference at time of diagnosis.
Functional neuroimaging of high-risk 6-month-old infants predicts a diagnosis of autism at 24 months of age
Emerson RW, Adams C, Nishino T, Hazlett HC, Wolff JJ, Zwaigenbaum L, Constantino JN, Shen MD, Swanson MR, Elison JT, Kandala S, Estes AM, Botteron KN, Collins L, Dager SR, Evans AC, Gerig G, Gu H, McKinstry RC, Paterson S, Schultz RT, Styner M; IBIS Network, Schlaggar BL, Pruett JR Jr, Piven J. Sci Transl Med.. 2017 Jun 7;9(393). pii: eaag2882. [PMID: 28592562]
ASD symptoms in young children are often evident by 24 months of age, but often children are diagnosed much later. Research has suggested that detection and intervention before 24 months of age can improve skills and abilities in children with ASD. Although infants as young as 6 months old can display behavioral differences that are related to ASD or other developmental disabilities, these behavioral signs are not strong or specific enough to predict an ASD diagnosis or differentiate it from other types of developmental delays. In this study, researchers used functional connectivity magnetic resonance imaging (fcMRI) to look at the brain connectivity of 6-month-old infants who had high familial risk of developing ASD (children with a high familial risk have about a 20% chance of developing ASD as compared to about a 1.5% chance for the general population). The goal of the study was to determine whether early fcMRI findings could predict a later ASD diagnosis at 24 months.
First, the researchers performed fcMRIs on 59 infants at 6 months old. Using an analysis of different brain regions, brain connections, and the relationship of those brain regions and connections to behaviors, the researchers identified areas of interest and used the analysis to develop a method to predict an ASD diagnosis. Later, when the infants reached 24 months old, the researchers tested the infants for ASD based on their social behavior, language, motor development, and repetitive behavior. They compared their ASD predictions from the fcMRI scans at 6 months with the outcomes of ASD diagnostic testing at 24 months.
Based on the testing at 24 months, 11 children received an ASD diagnosis. Of those 11 children, 9 diagnoses were correctly predicted by the fcMRI that was performed when the children were 6 months old. Likewise, all 48 children who did not receive an ASD diagnosis at 24 months were correctly predicted to test negative for ASD based on their fcMRI scans at 6 months old. Further, of the 26,335 neural connections studied from the fcMRI scan, the researchers identified 974 connections that differ between ASD and non-ASD children. Importantly, neural activity that was recorded in the brain regions of interest during the fcMRI scans corresponded with the behavioral differences that were observed in children at 24 months old.
The researchers conclude that neuroimaging at 6 months of age can accurately predict an ASD diagnosis, with greater than 96% accuracy. Recognizing, however, that diagnostic fcMRIs are too expensive to be widely used as ASD screening tools, the researchers suggest that future studies build on these findings to continue the development of more cost-effective early diagnostic methods.
Early brain development in infants at high risk for autism spectrum disorder
Hazlett HC, Gu H, Munsell BC, Kim SH, Styner M, Wolff JJ, Elison JT, Swanson MR, Zhu H, Botteron KN, Collins DL, Constantino JN, Dager SR, Estes AM, Evans AC, Fonov VS, Gerig G, Kostopoulos P, McKinstry RC, Pandey J, Paterson S, Pruett JR, Schultz RT, Shaw DW, Zwaigenbaum L, Piven J; IBIS Network; Clinical Sites; Data Coordinating Center; Image Processing Core; Statistical Analysis. Nature. 2017 Feb 15;542(7641):348-351. [PMID: 28202961]
Brain enlargement has been observed in children with ASD, and evidence suggests that changes in brain volume can be observed between 12 and 24 months of age. In this study, the researchers sought to determine whether changes in the brain volume of children younger than 24 months of age correspond with the onset of behavioral symptoms of ASD.
The researchers used a subset of data from an existing study, which consisted of 106 infants with high familial risk of developing ASD and 42 infants with low familial risk. The researchers used behavioral assessments and magnetic resonance imaging (MRI) to evaluate the infants for ASD at 6, 12, and 24 months of age. After the evaluation at 24 months, the researchers divided the participants into three groups: those with high familial risk who screened positive for ASD (HR-ASD), those with high familial risk who screened negative for ASD (HR-neg), and low-risk infants who screened negative for ASD (LR).
The researchers looked at the rate at which total brain volume (TBV) increased between 6 and 12 months of age and between 12 and 24 months of age. They found that the TBV growth rate between 12 and 24 months was significantly higher in the HR-ASD group than in the HR-neg or the LR group. No such difference was seen among the groups between 6 and 12 months of age. However, for infants diagnosed with ASD at 24 months, the increase in TBV was correlated with hyper-expansion of the surface area of the outer layer of the brain, called the cerebral cortex, in the first year of life.
The researchers next looked to see if the TBV growth rate corresponded with ASD severity to determine if faster growth rate indicates more severe ASD behavioral symptoms. They compared the change in TBV growth rate between 6 and 12 months and between 12 and 24 months with the Autism Diagnostic Observation Schedule (ADOS) score administered to the children at 24 months. The ADOS measures two types of behavioral domains: 1) Social Affect, which measures behaviors such as social gestures and eye contact and 2) Restricted and Repetitive Behaviors, which measures behaviors such as hand flapping, rituals, or sensory sensitivities. They found a significant relationship with the change in TBV growth rate between 12 and 24 months and the severity of symptoms in children measured by the ADOS score. The strongest correlation was between TBV growth rate and the ADOS Social Affect score, such that faster TBV growth was associated with a reduced number of typical social behaviors.
Lastly, the researchers determined whether specific brain measurements taken at 6 and 12 months of age could predict a positive ASD diagnosis at 24 months of age. They examined the change in cortical thickness (a measure of the thickness of the outer layer of the brain) and cortical surface area (a measurement of the folds in the outer layer of the brain) in HR-ASD and HR-neg infants between 6 and 12 months of age. They found that the rate at which cortical surface area increased was significantly higher in HR-ASD infants than in HR-neg infants. The greatest increase occurred in areas of the brain that control sensory information processing. This finding suggests that changes in brain growth rate between 6 and 12 months of age can predict changes in the brain that occur between 12 and 24 months of age and correspond with the development of ASD symptoms.
Together, these results provide potential predictive and diagnostic measures of the development of ASD, and shed light on the physical changes that correspond with behavioral differences during the critical period of ASD symptom emergence and diagnosis.
A prospective study of the concordance of DSM-IV and DSM-5 diagnostic criteria for autism spectrum disorder
Mazurek MO, Lu F, Symecko H, Butter E, Bing NM, Hundley RJ, Poulsen M, Kanne SM, Macklin EA, Handen BL. J Autism Dev Disord. 2017 Sep;47(9):2783-2794. [PMID: 28620892]
The Diagnostic and Statistical Manual of Mental Disorders (DSM) is a tool used to diagnose mental health disorders that is periodically updated to revise diagnostic criteria. ASD has been included in the DSM since the third edition (DSM-III) was released in 1980. The most recent revision from DSM-IV to DSM-5 has been met with some controversy. Specifically, the DSM-IV included subcategories of autism, including autistic disorder, pervasive developmental disorder not otherwise specified (PDD-NOS), and Asperger’s disorder. Revisions to the DSM-5 merged the subcategories of autism under a single category of ASD and changed parts of the diagnostic criteria.
The goal of this study was to compare the ASD diagnostic criteria of the DSM-IV and the DSM-5 to determine how changes in categories and criteria could affect the calculation of autism rates and inclusion in autism research. The participants were 439 children and adolescents who had previously been referred for a diagnostic evaluation for autism. Some of the children met diagnostic criteria for ASD based on the DSM-IV, the DSM-5, or both. Some of the children did not meet the criteria for ASD based on either version. Following several diagnostic assessments, clinicians completed a DSM-IV and DSM-5 checklist for each child to determine if the child met the criteria for ASD based on both versions of the DSM.
Of the 439 children evaluated, 278 met DSM-IV criteria for ASD (229 met criteria for autism, 25 met criteria for Asperger’s, and 24 met criteria for PDD-NOS), and 249 children met DSM-5 criteria. Thirty children met DSM-IV but not DSM-5 criteria, and one child met DSM-5 but not DSM-IV criteria. Of those that met DSM-IV but not DSM-5 criteria, 3% met criteria for autism, 20% met criteria for Asperger’s, and 75% met criteria for PDD-NOS.
The researchers performed statistical tests to compare the sensitivity (the ability of the diagnostic test to correctly identify people with ASD) and the specificity (the ability of the diagnostic test to correctly identify people without ASD) of the DSM-5 relative to the DSM-IV. They found that the DSM-5 showed near-perfect specificity (0.99) and a relatively high sensitivity (0.89) for ASD overall, and that both sensitivity and specificity were strongest for children who met criteria for autistic disorder. The DSM-5 was less sensitive for children with Asperger’s, and significantly less sensitive for children with PDD-NOS. Similarly, the DSM-5 was about half as specific for correctly identifying a child that does not have Asperger’s and PDD-NOS.
The researchers also looked at whether demographic factors, such as age, race, gender, intelligence scores, and parental education level affect the level of agreement between DSM-IV and DSM-5 diagnoses. They found that higher scores on intelligence tests were associated with discordance, or mismatching, of the DSM-5 criteria with the DSM-IV criteria. They also found that discordance was more likely between the two versions when assessing girls, highlighting the existing concern that females with ASD are under-identified.
The researchers concluded that the DSM-5 criteria are stricter than the DSM-IV criteria, particularly for diagnosis of Asperger’s and PDD-NOS, and that more subtle symptoms may be less likely to meet criteria. However, they also propose that the more stringent criteria established in the DSM-5 may result in more consistent diagnoses across clinicians, which may help ensure that services and support are better matched.