Cluster analysis of autism spectrum disorder symptomatology: Qualitatively distinct subtypes or quantitative degrees of severity of a single disorder?

doi:10.1016/j.ridd.2018.03.006

Research in Developmental Disabilities

Volume 76, May 2018, Pages 65-75

https://doi.org/10.1016/j.ridd.2018.03.006 Get rights and content

Abstract

The decision to collapse several related disorders into a single diagnosis of Autism Spectrum Disorder (ASD) generated significant controversy and debate. There has been mixed evidence as to whether various ASD subtypes are qualitatively distinct or if they exist on a spectrum of symptom severity. The present study conducted a two-step cluster analysis of major ASD symptoms in a sample of 147 young males with ASD aged between 6yr and 18yr with IQ > 70. Results indicated that a two-cluster solution (high and low severity of ASD symptomatology) was reliable and valid. Further, the construct of challenging behaviour was not a necessary component of the two-cluster solution, verifying the new conceptualisation of ASD. Further replication of these findings with other subsets of individuals with ASD is needed.

Section snippets

What this paper adds

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The ongoing clinical debate regarding the appropriate diagnostic classification protocol for Autism Spectrum Disorders (ASD) reflects confusion in the field. To help clarify this issue, Cluster Analytic techniques were used to form models of the diagnostic criteria for ASD in a sample of 147 young males with ASD. Results verified the recent DSM-5 model, excluding challenging behaviour as a major indicator of ASD. These findings assist in the accurate diagnosis and treatment planning for youth

Participants

In determining the required sample size for CA, two schools of thought exist. First, Formann (1984) recommended specific sample size calculations based on the number of variables (a minimum sample size of 2^k, where k is the number of variables) for performing latent class analysis, a related statistical technique, and some researchers have applied this procedure to sample size calculations for CA in the area of autism (McCrimmon, Schwean, Saklofske, Montgomery, & Brady, 2012). Second, Hair,

Data diagnostics

Prior to CA procedures, the data were screened for missing data, normality, the presence of outliers, and independence. The original sample consisted of 150 young males with ASD, but because two-step CA requires complete data on the clustering variables (ASD symptoms, SF, and CB), three cases with missing data were removed, resulting in a final sample size of 147. Data on the clustering variables were normally distributed at the total scale and subscale levels, and thus no data transformations

Implications of findings

The results of the CA in the present study have several implications. First, the CA that included CB as an indicator of ASD symptomatology in combination with core ASD symptoms (social deficits and restricted-repetitive behaviour) and SF (sensory difficulties) failed to successfully replicate, unlike the CA which included only core ASD symptoms and SF as clustering variables. This suggests that CB, which has previously been shown to be a significant associated clinical feature in children with

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Conflict of interest

The authors declare that they have no conflict of interest.

Informed consent

Informed consent was obtained from each of the parents who participated in the study, and verbal assent was obtained from their sons.

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