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Parents of children with autistic spectrum disorders (ASD) usually are told that the risk for recurrence in younger siblings ranges from 3%–10%. The wide range reflects different reporting methods and the tendency for parents to not have more children after the diagnosis of an affected child. An international research consortium prospectively followed 664 infants with older biological siblings with ASD until age 36 months; the 3-year-olds were evaluated for ASD with the most widely used standardized assessment (the Autism Diagnostic Observation Scale) and clinical assessment by an expert clinician.
Overall, 132 infant siblings (19%) received diagnoses of ASD; autistic disorder was diagnosed in 41% and pervasive developmental disorder was diagnosed in 59%. An ASD diagnosis was three times more likely in younger male siblings than in female siblings (26% vs. 9%) and twice as likely in siblings who had more than one affected sibling as in those who had only one affected sibling. IQ, severity of autism, race, ethnicity, birth order, and parental education did not predict outcome.
Ozonoff S et al. Recurrence risk for autistic spectrum disorders: A baby siblings research consortium study. Pediatrics 2011 Aug 15; [e-pub ahead of print]. (http://dx.doi.org/10.1542/peds.2010-2825)
Comment
The 19% rate of ASD among infants with older autistic siblings is higher than previously reported. The large sample size and prospective study design make these results credible. How do we use this information in pediatric practice to inform parents about the risk? Pediatricians who counsel parents about recurrence risk should be guided by the notion that “time is the currency of medicine.” This type of genetic information cannot be conveyed in a hurried manner. Active listening during the clinical encounter, recognition that counseling should be individualized to the needs of each family, and understanding the value of follow-up calls or visits can help enhance parental understanding.