Autistic disorder versus other pervasive developmental disorders in young children: same or different?

Investigating the borders of autism spectrum disorder: lessons from the former diagnosis of pervasive developmental disorder not otherwise specified

Introduction

Autism Spectrum Disorder (ASD) diagnosis is relatively consensual in typical forms. The margins of the spectrum and their degree of extension, however, are controversial. This has far-reaching implications, which extend beyond theoretical considerations: first, peripheral forms of autism are more prevalent than central forms; second, we do not know how relevant typical-targeted recommendations are for atypical forms. In DSM-IV-TR, these margins of autism were studied within the category of Pervasive Developmental Disorder - Not Otherwise Specified (PDD-NOS). In spite of its low reliability, this former diagnosis was of particular interest to shed light on the gray area of margins. The aim of this systematic is therefore to investigate the clinical characteristics of PDD-NOS in comparison with Autistic Disorder.

Method

A stepwise systematic PRISMA literature review was conducted by searching PubMed and Web Of Science databases to select corresponding studies.

Results

The systematic review included 81 studies comprising 6,644 children with PDD-NOS. Cross-sectional and longitudinal studies comparing PDD-NOS and AD showed that PDD-NOS corresponds to milder form of autism with less impact and less associated disorder, with the exception of schizophrenia and mood disorder.

Discussion

Our review challenges initial views of PDD-NOS, and shows the clinical relevance of this diagnosis when dealing with the margins of autism, and the de facto diversity included in the spectrum. However, in view of the many limitations of PDD-NOS (low reliability, instability through time, low acceptability), we suggest taxonomic changes in DSM-5: we introduce a new category based on three main dimensions related to socialization impairment, emotional lability and psychotic symptoms.

Conclusion

Our review argues for a distinction between AD and PDD-NOS on clinical characteristics and thus highlights the need to study the margins of autism. While the limitations of the PDD-NOS category made it irrelevant to investigate these margins from a research perspective, we believe that a multidimensional approach for mental health professionals taping socialization, emotion lability and psychotic symptoms would be interesting. Our review therefore encourage future studies to test relevant criteria for a new category and possibly identify developmental trajectories, specific interventions and treatments.

Severity of Autism Spectrum Disorders: Current Conceptualization, and Transition to DSM-5

Mirroring the evolution of the conceptualization of autism has been changes in the diagnostic process, including the most recent revisions to the DSM-5 and the addition of severity-based diagnostic modifiers assigned on the basis of intensity of needed supports. A review of recent literature indicates that in research stratifying individuals on the basis of autism severity, core ASD symptomology is the primary consideration. This conceptualization is disparate from the conceptualization put forth in DSM-5 in which severity determination is based on level of needed support, which is also impacted by cognitive, language, behavioral, and adaptive functioning. This paper reviews literature in this area and discusses possible instruments that may be useful to inform clinical judgment in determining ASD severity levels.

DSM-5 ASD moves forward into the past

The fifth edition of the diagnostic and statistical manual of mental disorders (DSM-5) (APA in diagnostic and statistical manual of mental disorders, Author, Washington, 2013) has decided to merge the subtypes of pervasive developmental disorders into a single category of autism spectrum disorder (ASD) on the assumption that they cannot be reliably differentiated from one another. The purpose of this review is to analyze the basis of this assumption by examining the comparative studies between Asperger's disorder (AsD) and autistic disorder (AD), and between pervasive developmental disorder not otherwise specified (PDDNOS) and AD. In all, 125 studies compared AsD with AD. Of these, 30 studies concluded that AsD and AD were similar conditions while 95 studies found quantitative and qualitative differences between them. Likewise, 37 studies compared PDDNOS with AD. Nine of these concluded that PDDNOS did not differ significantly from AD while 28 reported quantitative and qualitative differences between them. Taken together, these findings do not support the conceptualization of AD, AsD and PDDNOS as a single category of ASD. Irrespective of the changes proposed by the DSM-5, future research and clinical practice will continue to find ways to meaningfully subtype the ASD.

Brief report: an exploratory study comparing diagnostic outcomes for autism spectrum disorders under DSM-IV-TR with the proposed DSM-5 revision

The proposed revision for Autism spectrum disorders (ASDs) in the Diagnostic and Statistical Manual of Mental Disorders--Fifth Edition (DSM-5) represents a shift from the Diagnostic and Statistical Manual of Mental Disorders--Fourth Edition, Text Revision (DSM-IV-TR). As the proposed DSM-5 criteria require a higher minimum number of symptoms to be present compared to DSM-IV-TR, there have been some concerns about the impact that this will have on diagnostic outcomes. Therefore, the current study aimed to compare diagnostic outcomes using both DSM-IV-TR and DSM-5 criteria for 132 children. Of the 111 participants who received an ASD diagnosis under DSM-IV-TR, 26 did not meet DSM-5 criteria. The majority of these had received a DSM-IV-TR PDD-NOS diagnosis. Implications of the results and the proposed DSM-5 changes to the ASD criteria are discussed.

Is long-term prognosis for pervasive developmental disorder not otherwise specified different from prognosis for autistic disorder? Findings from a 30-year follow-up study

We followed 74 children with autistic disorder (AD) and 39 children with pervasive developmental disorder not otherwise specified (PDD NOS) for 17–38 years in a record linkage study. Rates of disability pension award, marital status, criminality and mortality were compared between groups. Disability pension award was the only outcome measure that differed significantly between the AD and PDD NOS groups (89% vs. 72%, p < 0.05). The lower rate of disability pension award in the PDD NOS group was predicted by better psychosocial functioning. The lack of substantial differences in prognosis between the groups supports a dimensional description of autism spectrum disorder, in line with proposed DSM-V revision.

Toward specifying pervasive developmental disorder-not otherwise specified

Pervasive developmental disorder-not otherwise specified (PDD-NOS) is the most common and least satisfactory of the PDD diagnoses. It is not formally operationalized, which limits its reliability and has hampered attempts to assess its validity. We aimed, first, to improve the reliability and replicability of PDD-NOS by operationalizing its DSM-IV-TR description and, second, to test its validity through comparison with autistic disorder (AD) and Asperger's disorder (AsD). In a sample of 256 young people (mean age = 9.1 years) we used Developmental, Diagnostic and Dimensional (3Di) algorithmic analysis to classify DSM-IV-TR AD (n = 97), AsD (n = 93) and PDD-NOS (n = 66). Groups were compared on independent measures of core PDD symptomatology, associated autistic features, and intelligence. Contrary to the assumption that PDD-NOS is heterogeneous, almost all (97%) of those with PDD-NOS had one distinct symptom pattern, namely impairments in social reciprocity and communication, without significant repetitive and stereotyped behaviors (RSB). Compared to AD and AsD, they had comparably severe but more circumscribed social communication difficulties, with fewer non-social features of autism, such as sensory, feeding and visuo-spatial problems. These individuals appear to have a distinct variant of autism that does not merely sit at the less severe end of the same continuum of symptoms. The current draft guidelines for DSM-V, which mandate the presence of RSBs for any PDD diagnosis, would exclude such people from the autistic spectrum.

Novel method for combined linkage and genome-wide association analysis finds evidence of distinct genetic architecture for two subtypes of autism

The Autism Genome Project has assembled two large datasets originally designed for linkage analysis and genome-wide association analysis, respectively: 1,069 multiplex families genotyped on the Affymetrix 10 K platform, and 1,129 autism trios genotyped on the Illumina 1 M platform. We set out to exploit this unique pair of resources by analyzing the combined data with a novel statistical method, based on the PPL statistical framework, simultaneously searching for linkage and association to loci involved in autism spectrum disorders (ASD). Our analysis also allowed for potential differences in genetic architecture for ASD in the presence or absence of lower IQ, an important clinical indicator of ASD subtypes. We found strong evidence of multiple linked loci; however, association evidence implicating specific genes was low even under the linkage peaks. Distinct loci were found in the lower IQ families, and these families showed stronger and more numerous linkage peaks, while the normal IQ group yielded the strongest association evidence. It appears that presence/absence of lower IQ (LIQ) demarcates more genetically homogeneous subgroups of ASD patients, with not just different sets of loci acting in the two groups, but possibly distinct genetic architecture between them, such that the LIQ group involves more major gene effects (amenable to linkage mapping), while the normal IQ group potentially involves more common alleles with lower penetrances. The possibility of distinct genetic architecture across subtypes of ASD has implications for further research and perhaps for research approaches to other complex disorders as well.

Maternal immune activation and autism spectrum disorder: interleukin-6 signaling as a key mechanistic pathway

An emerging area of research in autism spectrum disorder (ASD) is the role of prenatal exposure to inflammatory mediators during critical developmental periods. Epidemiological data has highlighted this relationship showing significant correlations between prenatal exposure to pathogens, including influenza, and the occurrence of ASD. Although there has not been a definitive molecular mechanism established, researchers have begun to investigate this relationship as animal models of maternal infection have support- ed epidemiological findings. Several groups utilizing these animal models have found that activation of the maternal immune system, termed maternal immune activation (MIA), and more specifically the exposure of the developing fetus to maternal cytokines precipitate the neurological, immunological and behavioral abnormalities observed in the offspring of these animals. These abnormalities have correlated with clinical findings of immune dysregulation, neurological and behavioral abnormalities in some autistic individuals. Additionally, researchers have observed genetic variations in these models in genes which regulate neurological and immunological development, similar to what is observed clinically in ASD. Altogether, the role of MIA and cytokine dysregulation, as a key mediator in the neuropathological, behavioral and possibly genetic irregularities observed clinically in autism are important factors that warrant further investigation.

Evidence for latent classes of IQ in young children with autism spectrum disorder

Autism is currently viewed as a spectrum condition that includes strikingly different severity levels; IQ is consistently described as one of the primary aspects of the heterogeneity in autism. To investigate the possibility of more than one distinct subtype of autism based on IQ both latent class analysis and taxometrics methods were used to classify Mullen IQs in a sample of 456 children with autism spectrum disorder. We found evidence for multiple IQbased subgroups using both methods. Groups differed in level of intellectual functioning and patterns of verbal versus nonverbal ability. Results support the notion of distinct subtypes of autism that differ in severity of intellectual ability, patterns of cognitive strengths and weaknesses, and severity of autism symptoms.

High Rates of Psychiatric Co-Morbidity in PDD-NOS

Rates of co-morbid psychiatric conditions in children with Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS) are hardly available, although these conditions are often considered as more responsive to treatment than the core symptoms of PDD-NOS. Ninety-four children with PDD-NOS, aged 6-12 years were included. The DISC-IV-P was administered. At least one co-morbid psychiatric disorder was present in 80.9% of the children; 61.7% had a co-morbid disruptive behavior disorder, and 55.3% fulfilled criteria of an anxiety disorder. Compared to those without co-morbid psychiatric disorders, children with a co-morbid disorder had more deficits in social communication. Co-morbid disorders occur very frequently in children with PDD-NOS, and therefore clinical assessment in those children should include assessment of co-morbid DSM-IV disorders.

Autism spectrum traits in children with mood and anxiety disorders

The autism spectrum disorders (ASDs) can present with symptoms commonly found in mood and anxiety disorders. The Social Communication Questionnaire (SCQ), Children's Communication Checklist (CCC-2), and the Social Reciprocity Scale (SRS) were used to screen children in a mood disorders research clinic setting for symptoms of ASD. Ninety-three patients (mean age, 12.7 +/- 2.8 years; percent male, 63%) completed at least one scale, and 50 children completed all three. The prevalence of those screening positive for a possible ASD on one instrument was 62% and on all three measures was 8%. Fifty-seven percent (n = 21/37; odds ratio, 4.59 [95% confidence interval (CI) = 1.40-15.11]) of those scoring in the "ASD-likely" range on the SRS scored in that range on the CCC-2. Only 16% (n = 6/37; odds ratio, not significant (NS)) of those scoring in the ASD-likely range on the SRS, and 14% (n = 5/37; odds ratio, NS) of those scoring in the ASD-likely range on the CCC-2, scored similarly on the SCQ. These results demonstrate a need to develop valid and reliable instruments to screen for ASDs in children presenting outside of ASD clinics.

Specifying PDD-NOS: a comparison of PDD-NOS, Asperger syndrome, and autism

OBJECTIVE

To describe the clinical characteristics of children given a diagnosis of pervasive developmental disorder-not otherwise specified (PDD-NOS) by expert clinicians and to compare these to the clinical characteristics of children given a diagnosis of autism and Asperger syndrome (AS).

METHOD

Two hundred sixteen children with autism, 33 with AS, and 21 with PDD-NOS were compared on measures of level of functioning (communication, daily living and social skills, IQ, and age of acquisition of language) and on various symptoms of autism (impaired communication and reciprocal social interaction and a preference for repetitive and stereotyped activities).

RESULTS

In terms of level of functioning measures, the PDD-NOS children had scores that were between those of the children with autism and those of the children with AS. In contrast, the PDD-NOS group had fewer autistic symptoms, especially repetitive stereotyped behaviors, than both the autism and AS groups (chi2 = 11.06, p =.004). Children with PDD-NOS could be placed into one of three subgroups: a high-functioning group (24%) who resembled AS but had transient language delay or mild cognitive impairment; a subgroup resembling autism (24%) but who had late age of onset or too severe cognitive delays or were too young to potentially meet the full diagnostic criteria for autism; and a group (52%) not fulfilling the criteria for autism because of fewer stereotyped and repetitive behaviors.

CONCLUSIONS

With some revision to current diagnostic criteria, a more homogenous atypical group with significant impairments in social-communication but fewer repetitive behaviors can be differentiated from the more nonspecific PDD-NOS group. This differentiation may lead to better reliability in diagnosis and to further progress in studies of etiology.

Preschool children with autism spectrum disorders in Taiwan: follow-up of cognitive assessment to early school age

In this study, we longitudinally followed into childhood a cohort of preschool children, initially diagnosed as autistic or non-autistic with developmental delay, to evaluate the stability of cognitive assessments performed during the preschool period. The consistency in group means and intra-individual stability of developmental quotients (DQ) and non-verbal intelligence quotients (IQs) were compared for these two groups, which were matched by chronological age, initial non-verbal IQ/DQs, initial test given, and length of follow-up interval. The case group comprised 16 autistic children with average age at initial assessment of 3 years 8 months. The control group comprised 16 non-autistic developmental delayed children with average age at initial assessment of 3 years 11 months. Mean DQ/non-verbal IQ at initial assessment was 73.9+/-23.9 for the case group and 80.3+/-23.2 for the control group. ANOVA yielded no significant effect of time or time x diagnosis interaction (F=0.183, P=0.675). The absolute difference in scores and group means were equivalent for both groups of children, with no difference in patterns of change. Correlations between DQ/non-verbal IQs at initial assessment and follow-up were significant and high for the two groups (autistic group: r=0.87; control: r=0.77). Intellectual functioning can be a valid measure in Taiwanese preschool children with autism, and has an equivalent meaning for children with autism and for non-autistic children with developmental delay. Though the follow-up period is too short for definite prognostic conclusions to be drawn, we think that non-verbal intelligence should be an essential assessment for preschool oriental autistic children so that sound expectation and treatment plan can be made.

Autism spectrum disorders: update of evaluation and treatment

Autistic spectrum disorders are a group of neurodevelopmental conditions that are increasingly capturing the attention of clinicians and investigators. New insights from genetics and neuropathophysiology of autism will increasingly inform treatment. Presently, individualized treatment approaches typically include a mix of behavioral and, occasionally, pharmacotherapeutic strategies. Concerning the latter, exquisite sensitivity to medication is not uncommon in some children with autism.