Autism: Early Screening, Intervention Imperative
Mahoney, Diana, Clinical Psychiatry News
When it comes to understanding autism, more questions remain than answers. But the importance of early intervention is a certainty.
Numerous studies have shown that appropriate behavioral interventions implemented early and aggressively in children diagnosed with autism or an autism spectrum disorder (ASD) can improve the daily and long-term functioning and intellectual development of these children.
Such interventions also have the potential to minimize the incidence or severity of comorbid mental health problems.
The ability to intervene early, however, hinges on early identification. And although mounting evidence shows that autism can be diagnosed in young toddlers and potentially in infants, evidence also shows that screening advances developed in academic research centers have yet to filter to clinical practice.
The complex and variable nature of autism and its related disorders certainly makes diagnosing these conditions difficult. Without definitive biological markers, clinicians are left to rely primarily on parental reports and direct observation.
Yet, despite the diagnostic obstacles, studies show that standardized tools can effectively screen for autistic behaviors in young children. For example, investigators in Hong Kong recently showed that an instrument called CHAT-23 was a highly sensitive and specific screen for autism in a cohort of 212 developmentally delayed Chinese children with mental ages of 18-24 months.
A combination of two earlier tests--the Checklist for Autism in Toddlers (CHAT) and the modified CHAT (mCHAT)--CHAT-23 consists of a self-administered parent questionnaire that addresses social interest, motor development, social play, pretend play, the use of pointing to ask for or show something, and rough-and-tumble play. Additionally, the measure includes a clinician observation component that looks at five actions: eye contact, ability to follow a point, and pretend play (Pediatrics 2004;114:el66-76).
Through the study, the investigators identified seven key questions on the parental questionnaire that could best discriminate autism from nonautism, addressing areas of joint attention, pretend play, social relatedness, and social referencing. Failing any two of the seven questions yielded a sensitivity of 0.931 and specificity of 0.768.
On the clinician observational component, all items but the block tower activity were found to discriminate autism from nonautism. Failing any two of the remaining four items produced a sensitivity of 0.736 and a specificity of 0.912.
The CHAT-23 and most other autism screening instruments were designed to screen children 18 months and older. New tools are being developed to screen younger children. In a landmark study in Canada, for example, researchers were able to pinpoint specific behavioral signs in infants as young as 12 months that can accurately predict whether a child will develop autism (Int. J. Devl. Neurosci. 2005;23:143-52).
The investigators developed an instrument called the Autism Observation Scale for Infants (AOSI) and tested it in a cohort of infant siblings of autistic children. The AOSI maps the development of infants as young as 6 months against 16 risk markers for autism.
According to Dr. Lonnie Zwaigenbaum, a developmental pediatrician at McMaster University in Hamilton, Ont., and one of the lead investigators in what is now called the Canada/U.S. Baby Sibs Research Consortium, the investigation showed that "the predictive power of these markers is remarkable." Within this high-risk group of children, "almost all of the children diagnosed with autism by age 2 had seven or more of the predictive markers by the time they were a year old," Dr. Zwaigenbaum said.
Certain behaviors that were present as early as age 6 months distinguished those children who were later diagnosed with autism from their nonautistic peers in the study. …