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Reliability and Validity of the Autism Spectrum Addendum to the Anxiety Disorders Interview Schedule (ADIS/ASA)
Objectives: To assess inter-rater reliability as well as convergent and discriminant validity of the ADIS/ASA.
Methods: The parents of 70 cognitively-able (IQ>70) children (ages 8-13 years, Mage=10.67, SD=1.64) with ASD completed the ADIS/ASA along with a battery of other behavioral measures as part of a screening evaluation for a randomized clinical trial comparing two cognitive-behavioral therapies for anxiety. A second rater independently observed and scored recordings of the original interviews. Inter-rater reliability as well as convergent and discriminant validity of the ADIS/ASA with other measures were assessed.
Results: Inter-rater agreement for specific ASA items (ICC=.82-.96), traditional anxiety (ICC=.85-.98), and ambiguous anxiety severity ratings (ICC=.87-.95) was excellent. Agreement was also good to excellent regarding principal diagnoses (κ =.82), the presence of clinically significant traditional anxiety (κ =.67-.91), and ambiguous anxiety (κ =.77-.90). Pearson correlations indicated convergence of the most severe ADIS/ASA anxiety severity ratings (traditional or ambiguous) with Pediatric Anxiety Rating Scale totals (PARS; r=.52, p<.01). ADIS/ASA traditional anxiety ratings converged with the Child Behavior Checklist (CBCL) anxiety subscale (r=.35, p<.01), but diverged from Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) comparison scores (r=-.02, n.s.) and CBCL Attention (r=.023, n.s.) and Aggression subscales (r=-.16, n.s). By comparison, the severity of ambiguous ADIS/ASA symptoms was significantly correlated with ADOS-2 severity ratings (r=.31, p<.02), but not the CBCL anxiety (r=.03, n.s.), Attention (r=.08, n.s.) or Aggression (r=.11, n.s.) subscales.
Conclusions: Findings indicate that the ADIS/ASA provides consistent measurement of traditional as well as more ambiguous anxiety-like symptoms in children with ASD across different raters. Additionally, the ADIS/ASA shows adequate convergent and discriminant validity with other measures. Implications for future studies of the treatment, prevalence and phenomenology of anxiety in ASD will be discussed.