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Characteristics of Autism Spectrum Disorder Surveillance Cases without a Community Diagnosis: Missouri Autism and Developmental Disabilities Monitoring Network, 2006-2008

Thursday, 2 May 2013: 09:00-13:00
Banquet Hall (Kursaal Centre)
R. Fitzgerald1, E. Molloy2 and J. N. Constantino3, (1)Washington University School of Medicine, St. Louis, MO, (2)Washington University in St. Louis, Harrison, OH, (3)Washington University School of Medicine, Saint Louis, MO
Background:  The Autism and Developmental Disabilities Monitoring (ADDM) Network is population-based surveillance system that identifies children with autism spectrum disorders (ASD) in multiple areas of the United States by reviewing evaluations (from birth through 8 years of age) contained in medical and/or educational records of children in a defined population.  The ADDM methods do not require a documented diagnosis of ASD to assign an ASD case status, therefore some ADDM ASD cases do not have a documented ASD diagnosis in their surveillance record.

Objectives:  To characterize Missouri ADDM surveillance ASD cases without a documented ASD diagnosis.

Methods:  The Missouri ADDM site’s surveillance area consists of 5 counties in the metropolitan St. Louis area. This analysis was limited to Missouri (MO) ADDM ASD cases from surveillance years 2006 and 2008. We created a dichotomous variable indicating whether or not an ASD case had a documented ASD diagnosis by a community provider. Univariate analyses were conducted to compare ASD cases with and without at community ASD diagnosis on various demographic, surveillance, and diagnostic variables. A χ2 test was used for categorical variables. The Wilcoxon Scores test was used to compare distributions of continuous variables for the two groups. We created a logistic regression model to generate adjusted odds ratios for select variables.

Results: A total of 678 8 year-old children met the MO ADDM case definition for.  124/678 (18.2%) of these cases had no abstracted community diagnosis.  Only 66/124 (53%) had any mention of ASD on an abstracted evaluation. There were no differences between ASD cases with a community diagnosis vs.  those without  on gender, race, age at first evaluation, presence of general developmental delay or social delay  before 36 months. Cases without a community diagnosis were more likely to have fewer abstracted evaluations (median of 3 vs. 5, p<.0001),  a comorbid ADDM classification of cerebral palsy (CP) (7.3% vs. 2.0%, p=0.002), and an ASD-NOS rather than Autism ADDM case classification (32.3% vs. 21.7%, p=0.012).  ADDM cases without a community diagnosis were also less likely to have a developmental language (χ2 =8.089, df=1, p=0.005)or  play delay(χ2 =4.100, df=1, p=0.043)  documented before the age of 3 years. The final logistic regression model (modeling probability of no community diagnosis) contained the following variables: age at first eval (OR= 0.984, 95% CI, 0.973,0.994), number of abstracted evalutions (OR= 0.830, 95% CI, 0.766,0.900), co-morbid cerebral palsy (OR= 3.964, 95% CI, 1.541,10.200), documented regression (OR= 0.461, 95% CI, 0.256,0.831), and presence of language delay prior to 3 years (OR= 0.547, 95% CI, 0.333,0.899). 

Conclusions: Nearly 20% of MO ADDM ASD cases did not have a documented community. The odds of having documented regression or a language delay before 3 years were approximately 50% less for ASD cases without a community diagnosis suggesting perhaps less severe ASD symptomology. Additionally, the odds of co-morbid CP was nearly 4 times higher for cases without a documented diagnosis. This suggests that ASD may be under-diagnosed in children with other developmental disabilities like CP.

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