Factors That Promote Early ASD Diagnosis Among Simplex Families in an Urban Setting

Background:  

Early diagnosis of ASD and subsequent intervention have been found to significantly and positively impact child outcomes (Zwaigenbaum et al., 2015).  It is unclear, however, which factors promote early diagnosis.  Studies have focused on environmental factors (e.g., poverty, accessibility of services, presence of an older sibling with ASD), but little is known about the biological and behavioral factors that may impact early diagnosis (Herlihy et al., 2015; Liptak et al., 2008).  Recent advances in the understanding of the genetic factors implicated in autism also necessitate an examination of the relationship between genetic status and age at diagnosis. 

Objectives:  

To determine the factors that promote early ASD diagnosis for children in simplex families within a homogeneous socio-demographic community. 

Methods:  

Participants included 182 children with ASD (79.9% male, mean age = 9.41 years) from the University of Washington’s Simons Simplex Collection (SSC) site.  28 children had an identified Likely Gene-Disrupting Mutation (LGD), while 154 were without an LGD.  Age of diagnosis was extracted from an interview used to qualify subjects for study participation. Child variables hypothesized to impact age at diagnosis included gender, presence of an LGD, developmental regression, and intellectual ability.  Presence of regression was extracted from the ADI-R, as was age at first parental concern.  Intellectual ability was assessed via full-scale IQ.  Demographic characteristics hypothesized to affect age at diagnosis were obtained from the SSC Background History Form.  To account for multiple comparisons during correlation and regression analyses, a stricter p-value of p<.008 was used.

Results:  

Bivariate correlations were performed using variables of interest and age at diagnosis.  Significant positive correlations between age at diagnosis and both age at parental concern and intellectual ability were identified (r(166) = .25, p=.000; r(166) = .353, p=.000).  Results indicated significant negative correlations between age at diagnosis and regression, r(166) = -.30, p=.000. Multiple linear regression was performed to assess which variables had the strongest effect on age at diagnosis.  There was a main effect of intellectual ability on age at diagnosis (B = .448, t(128) = 3.31, p=.001).  A trend suggested age at parental concern also predicted age at diagnosis (B = .596, t(128) = 2.37, p=.02). There was no main effect for any demographic characteristic. 

Conclusions:  

When environmental factors like income, education, and geographic access to services are consistent, children’s intellectual ability, a characteristic not specific to autism, may affect when children are diagnosed.  Additionally, while parental concern has not, historically, been shown to promote early ASD diagnosis, it appears to contribute to age at diagnosis in this sample, likely driven by similar factors (e.g., intellectual impairments are identified earlier).  Since having an older sibling with ASD has been shown to promote early diagnosis, focusing on simplex families gives important insight into the factors that impact diagnosis when families do not have prior ASD experience.  The results indicate a need for parent education to help parents recognize ASD symptoms, specifically for those children who may not exhibit other developmental delays.