Autism prodrome 17 of 89
Of the 58 children who failed on both administrations of the M-CHAT, 39
subsequently received an ASD diagnosis and the remaining 19 were found to have
language or global developmental delay. Note that only 3 of the 39 children with ASD
were from the unselected population, with the majority being identified from the
sample referred for early intervention services. Robins et al. (2001) found that the
items that best discriminated between children with ASD and children with other
developmental problems were those that measured joint attention behaviors (pointing
and following a point, bringing things to show), social relatedness (interest in other
children, imitation) and communication (response to name). Robins et al. (2001)
calculated sensitivity, specificity and positive predictive values for various
combinations of M-CHAT items and demonstrated that in this largely referred sample
its instrument parameters were strong. A recent study (Kleinman et al., 2008) has
reported on the M-CHAT with a new sample of 3,793 children aged 16 to 30 months.
Kleinman and colleagues found a positive predictive value of 0.36 for the initial
screening which improved to 0.74 for the screening plus the follow-up telephone
interview. Again, most cases were identified from the ‘high risk’ sample of children
referred for early intervention services or due to a developmental concern. Follow-up
studies will allow us to estimate the instrument's parameters when used on an
unselected population, in particular its sensitivity in detecting cases of ASDs in
children about whom there had not been previous developmental concerns which
would constitute a better test of prodromal signs, as opposed to early emerging (and
recognized) signs of the disorder itself.
Wetherby and colleagues (Wetherby, Brosnan-Maddox, Peace, & Newton,
2008; Wetherby et al., 2004) have also developed an early screening tool that can be
used from 6 to 24 months of age - the Infant Toddler Checklist (ITC). The ITC is a